* [PATCH] Use C99-compliant scanf under _GNU_SOURCE with C99/C++11 and higher.
@ 2018-12-17 16:53 Zack Weinberg
2018-12-17 16:59 ` Andreas Schwab
2018-12-17 17:01 ` Florian Weimer
0 siblings, 2 replies; 6+ messages in thread
From: Zack Weinberg @ 2018-12-17 16:53 UTC (permalink / raw)
To: libc-alpha; +Cc: adhemerval.zanella
This is a rebased version of a patch I posted back in February. There
are no substantial code changes. I would like to see this get into 2.29
as it removes a C99 conformance defect for programs using _GNU_SOURCE.
Implementation notes:
There needs to be an internal override so we can compile the
noncompliant scanf itself. This is the same problem we had when we
removed 'gets' from _GNU_SOURCE and it's dealt with the same way:
there's a new __GLIBC_USE symbol, DEPRECATED_SCANF, which defaults to
off under the appropriate conditions for external code, but can be
overridden by individual files within stdio.
We also run into problems with PLT bypass, because libc_hidden_proto
uses __REDIRECT and so does the logic in stdio.h for choosing which
implementation of scanf to use; __REDIRECT isn't transitive, so a
couple of files that use sscanf internally have to bridge the gap
with macros. I'm open to better ideas if anyone has one. (I would
be in favor of a general policy that internal code should not use
any of the *scanf functions, but that would be nontrivial for
tzset.c.) Fortunately, elf/check-localplt will catch any new
internal uses of *scanf that aren't shimmed.
On a related note, the interaction of the C99/not-C99 scanf redirect
with the __LDBL_COMPAT scanf redirect was complicated, confusing,
and possibly wrong. The __ldbl_is_dbl cleanup (thanks to Gabriel
Gomes for finishing that for me) has made it less complicated, but
I'm still not 100% sure it's correct, and I do not have access to
physical hardware for which __LDBL_COMPAT is relevant, so my ability
to test it is limited. Careful review (you'll want to read all of
libio/bits/stdio-ldbl.h to understand what's going on, not just
the diff) and maybe even some volunteer testing would be appreciated.
Finally, there are several tests in stdio-common that use the
extension. bug21 is a regression test for a crash, and still
exercises the relevant code if changed to use %ms instead of %as.
scanf14 through scanf17 are more complicated since they are actually
testing the subtleties of the extension - under what circumstances is
'a' treated as a modifier letter, etc. My approach here is to
duplicate scanf14.c and scanf16.c; the originals change to use %ms
instead, the copies select precisely the right conformance mode to get
%as with the old GNU meaning, plus everything else they need (it's not
as simple as saying -std=gnu89, unfortunately). scanf15 and scanf17
become simpler because they no longer need to avoid _GNU_SOURCE, and
all of them no longer need diagnostic overrides. Yay!
--- 8< ---
The only difference between noncompliant and C99-compliant scanf is
that the former accepts the archaic GNU extension '%as' (also %aS and
%a[...]) meaning to allocate space for the input string with malloc.
This extension conflicts with C99's use of %a as a format _type_
meaning to read a floating-point number; POSIX.1-2008 standardized
equivalent functionality using the modifier letter 'm' instead (%ms,
%mS, %m[...]).
The extension was already disabled in most conformance modes:
specifically, any mode that doesn't involve _GNU_SOURCE and _does_
involve either strict conformance to C99 or loose conformance to both
C99 and POSIX.1-2001 would get the C99-compliant scanf. With
compilers new enough to use -std=gnu11 instead of -std=gnu89, or
equivalent, that includes the default mode.
This patch tightens things up further: you now get C99-compliant scanf
in all configurations except when _GNU_SOURCE is defined *and*
__STDC_VERSION__ or __cplusplus (whichever is relevant) indicates
C89/C++98. This leaves the old scanf available under e.g. -std=c89
-D_GNU_SOURCE, but removes it from e.g. -std=gnu11 -D_GNU_SOURCE (it
was already not present under -std=gnu11 without -D_GNU_SOURCE) and
from -std=gnu89 without -D_GNU_SOURCE.
* include/features.h (__GLIBC_USE_DEPRECATED_SCANF): New __GLIBC_USE
parameter. Only use deprecated scanf when __USE_GNU is defined
and __STDC_VERSION__ is less than 199901L or __cplusplus is less
than 201103L, whichever is relevant for the language being compiled.
* libio/stdio.h, libio/bits/stdio-ldbl.h: Decide whether or
not to redirect scanf, fscanf, sscanf, vscanf, vfscanf, and
vsscanf to their __isoc99_ variants based only on
__GLIBC_USE(DEPRECATED_SCANF).
* libio/iovsscanf.c, libio/vscanf.c, stdio-common/fscanf.c
* stdio-common/scanf.c, stdio-common/vfscanf.c:
Override __GLIBC_USE_DEPRECATED_SCANF to 1.
* stdio-common/sscanf.c: Likewise. Remove ldbl_hidden_def for
__sscanf.
* stdio-common/isoc99_sscanf.c: Add libc_hidden_def for __isoc99_sscanf.
* include/stdio.h: Provide libc_hidden_proto for __isoc99_sscanf,
not sscanf.
* misc/mntent_r.c, time/tzset.c: Redirect sscanf to __isoc99_scanf
with a macro.
* stdio-common/bug21.c, stdio-common/scanf14.c:
Use %ms instead of %as, %mS instead of %aS, %m[] instead of %a[];
remove DIAG_IGNORE_NEEDS_COMMENT for -Wformat.
* stdio-common/scanf16.c: Likewise. Add __attribute__((format(scanf)))
to xscanf, xfscanf, xsscanf.
* stdio-common/scanf14a.c: New copy of scanf14.c which still uses
%as, %aS, %a[]. Use conformance mode -std=gnu89,
_POSIX_C_SOURCE=199506L, _XOPEN_SOURCE=1, _XOPEN_SOURCE_EXTENDED=1,
which will use the nonconformant scanf implementation.
Remove DIAG_IGNORE_NEEDS_COMMENT for -Wformat.
* stdio-common/scanf16a.c: New copy of scanf16.c which still uses
%as, %aS, %a[]. Use conformance mode -std=gnu89,
_POSIX_C_SOURCE=199506L, _XOPEN_SOURCE=1, _XOPEN_SOURCE_EXTENDED=1,
_ISOC99_SOURCE=1, which will use the nonconformant scanf
implementation. Add __attribute__((format(scanf))) to xscanf,
xfscanf, xsscanf.
* stdio-common/scanf15.c, stdio-common/scanf17.c: No need to
override feature selection macros or provide definitions of u_char etc.
* stdio-common/Makefile (tests): Add scanf14a and scanf16a.
(CFLAGS-scanf15.c, CFLAGS-scanf17.c): Remove.
(CFLAGS-scanf14a.c, CFLAGS-scanf16a.c): New.
---
NEWS | 17 ++++
include/features.h | 22 +++++
include/stdio.h | 2 +-
libio/bits/stdio-ldbl.h | 7 +-
libio/iovsscanf.c | 5 ++
libio/stdio.h | 22 ++---
libio/vscanf.c | 5 ++
misc/mntent_r.c | 4 +
stdio-common/Makefile | 14 ++--
stdio-common/bug21.c | 11 +--
stdio-common/fscanf.c | 5 ++
stdio-common/isoc99_sscanf.c | 1 +
stdio-common/scanf.c | 5 ++
stdio-common/scanf14.c | 35 ++------
stdio-common/scanf14a.c | 126 ++++++++++++++++++++++++++++
stdio-common/scanf15.c | 14 +---
stdio-common/scanf16.c | 20 +++--
stdio-common/scanf16a.c | 156 +++++++++++++++++++++++++++++++++++
stdio-common/scanf17.c | 14 +---
stdio-common/sscanf.c | 6 +-
stdio-common/vfscanf.c | 5 ++
time/tzset.c | 4 +
22 files changed, 408 insertions(+), 92 deletions(-)
create mode 100644 stdio-common/scanf14a.c
create mode 100644 stdio-common/scanf16a.c
diff --git a/NEWS b/NEWS
index ae80818df4..fbe28f3270 100644
--- a/NEWS
+++ b/NEWS
@@ -62,6 +62,23 @@ Deprecated and removed features, and other changes affecting compatibility:
used by the Linux kernel. This affects the size and layout of those
structures.
+* An archaic GNU extension to scanf, under which '%as', '%aS', and '%a[...]'
+ meant to scan a string and allocate space for it with malloc, is now
+ restricted to programs compiled in C89 or C++98 mode with _GNU_SOURCE
+ defined. This extension conflicts with C99's use of '%a' to scan a
+ hexadecimal floating-point number, which is now available to programs
+ compiled as C99 or C++11 or higher, regardless of _GNU_SOURCE.
+
+ POSIX.1-2008 includes the feature of allocating a buffer for string input
+ with malloc, using the modifier letter 'm' instead. Programs using
+ '%as', '%aS', or '%a[...]' with the old GNU meaning should change to
+ '%ms', '%mS', or '%m[...]' respectively. Programs that wish to use the
+ C99 '%a' no longer need to avoid _GNU_SOURCE.
+
+ GCC's -Wformat warnings can detect most uses of this extension, as long
+ as all functions that call vscanf, vfscanf, or vsscanf are annotated with
+ __attribute__ ((format (scanf, ...))).
+
Changes to build and runtime requirements:
* Python 3.4 or later is required to build the GNU C Library.
diff --git a/include/features.h b/include/features.h
index 5bed0a4996..e6177f80f9 100644
--- a/include/features.h
+++ b/include/features.h
@@ -140,6 +140,7 @@
#undef __USE_FORTIFY_LEVEL
#undef __KERNEL_STRICT_NAMES
#undef __GLIBC_USE_DEPRECATED_GETS
+#undef __GLIBC_USE_DEPRECATED_SCANF
/* Suppress kernel-name space pollution unless user expressedly asks
for it. */
@@ -401,6 +402,27 @@
# define __GLIBC_USE_DEPRECATED_GETS 1
#endif
+/* GNU formerly extended the scanf functions with modified format
+ specifiers %as, %aS, and %a[...] that allocate a buffer for the
+ input using malloc. This extension conflicts with ISO C99, which
+ defines %a as a standalone format specifier that reads a floating-
+ point number; moreover, POSIX.1-2008 provides the same feature
+ using the modifier letter 'm' instead (%ms, %mS, %m[...]).
+
+ We now follow C99 unless GNU extensions are active and the compiler
+ is specifically in C89 or C++98 mode (strict or not). For
+ instance, with GCC, -std=gnu11 will have C99-compliant scanf with
+ or without -D_GNU_SOURCE, but -std=c89 -D_GNU_SOURCE will have the
+ old extension. */
+#if defined __USE_GNU && \
+ (defined __cplusplus \
+ ? (__cplusplus < 201103L && !defined __GXX_EXPERIMENTAL_CXX0X__) \
+ : (!defined __STDC_VERSION__ || __STDC_VERSION__ < 199901L))
+# define __GLIBC_USE_DEPRECATED_SCANF 1
+#else
+# define __GLIBC_USE_DEPRECATED_SCANF 0
+#endif
+
/* Get definitions of __STDC_* predefined macros, if the compiler has
not preincluded this header automatically. */
#include <stdc-predef.h>
diff --git a/include/stdio.h b/include/stdio.h
index 1b7da0f74d..a080b0730e 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -64,6 +64,7 @@ extern int __isoc99_vscanf (const char *__restrict __format,
extern int __isoc99_vsscanf (const char *__restrict __s,
const char *__restrict __format,
__gnuc_va_list __arg) __THROW;
+libc_hidden_proto (__isoc99_sscanf)
libc_hidden_proto (__isoc99_vsscanf)
libc_hidden_proto (__isoc99_vfscanf)
@@ -171,7 +172,6 @@ libc_hidden_proto (__dprintf)
libc_hidden_proto (fprintf)
libc_hidden_proto (vfprintf)
libc_hidden_proto (sprintf)
-libc_hidden_proto (sscanf)
libc_hidden_proto (fwrite)
libc_hidden_proto (perror)
libc_hidden_proto (remove)
diff --git a/libio/bits/stdio-ldbl.h b/libio/bits/stdio-ldbl.h
index 99d9bcc233..dfcbe5375a 100644
--- a/libio/bits/stdio-ldbl.h
+++ b/libio/bits/stdio-ldbl.h
@@ -26,9 +26,7 @@ __LDBL_REDIR_DECL (sprintf)
__LDBL_REDIR_DECL (vfprintf)
__LDBL_REDIR_DECL (vprintf)
__LDBL_REDIR_DECL (vsprintf)
-#if defined __USE_ISOC99 && !defined __USE_GNU \
- && !defined __REDIRECT \
- && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
+#if !__GLIBC_USE (DEPRECATED_SCANF)
__LDBL_REDIR1_DECL (fscanf, __nldbl___isoc99_fscanf)
__LDBL_REDIR1_DECL (scanf, __nldbl___isoc99_scanf)
__LDBL_REDIR1_DECL (sscanf, __nldbl___isoc99_sscanf)
@@ -44,8 +42,7 @@ __LDBL_REDIR_DECL (vsnprintf)
#endif
#ifdef __USE_ISOC99
-# if !defined __USE_GNU && !defined __REDIRECT \
- && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
+# if !__GLIBC_USE (DEPRECATED_SCANF)
__LDBL_REDIR1_DECL (vfscanf, __nldbl___isoc99_vfscanf)
__LDBL_REDIR1_DECL (vscanf, __nldbl___isoc99_vscanf)
__LDBL_REDIR1_DECL (vsscanf, __nldbl___isoc99_vsscanf)
diff --git a/libio/iovsscanf.c b/libio/iovsscanf.c
index ee6a99ec6a..69de5a09b6 100644
--- a/libio/iovsscanf.c
+++ b/libio/iovsscanf.c
@@ -24,6 +24,11 @@
This exception applies to code released by its copyright holders
in files containing the exception. */
+/* This file defines one of the deprecated scanf variants. */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
#include "strfile.h"
int
diff --git a/libio/stdio.h b/libio/stdio.h
index 739e08610d..86e7015655 100644
--- a/libio/stdio.h
+++ b/libio/stdio.h
@@ -399,13 +399,11 @@ extern int scanf (const char *__restrict __format, ...) __wur;
extern int sscanf (const char *__restrict __s,
const char *__restrict __format, ...) __THROW;
-#if defined __USE_ISOC99 && !defined __USE_GNU \
- && (!defined __LDBL_COMPAT || !defined __REDIRECT) \
- && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
+/* For historical reasons, the C99-compliant versions of the scanf
+ functions are at alternative names. When __LDBL_COMPAT is in
+ effect, this is handled in bits/stdio-ldbl.h. */
+#if !__GLIBC_USE (DEPRECATED_SCANF) && !defined __LDBL_COMPAT
# ifdef __REDIRECT
-/* For strict ISO C99 or POSIX compliance disallow %as, %aS and %a[
- GNU extension which conflicts with valid %a followed by letter
- s, S or [. */
extern int __REDIRECT (fscanf, (FILE *__restrict __stream,
const char *__restrict __format, ...),
__isoc99_fscanf) __wur;
@@ -447,13 +445,9 @@ extern int vsscanf (const char *__restrict __s,
const char *__restrict __format, __gnuc_va_list __arg)
__THROW __attribute__ ((__format__ (__scanf__, 2, 0)));
-# if !defined __USE_GNU \
- && (!defined __LDBL_COMPAT || !defined __REDIRECT) \
- && (defined __STRICT_ANSI__ || defined __USE_XOPEN2K)
-# ifdef __REDIRECT
-/* For strict ISO C99 or POSIX compliance disallow %as, %aS and %a[
- GNU extension which conflicts with valid %a followed by letter
- s, S or [. */
+/* Same redirection as above for the v*scanf family. */
+# if !__GLIBC_USE (DEPRECATED_SCANF)
+# if defined __REDIRECT && !defined __LDBL_COMPAT
extern int __REDIRECT (vfscanf,
(FILE *__restrict __s,
const char *__restrict __format, __gnuc_va_list __arg),
@@ -467,7 +461,7 @@ extern int __REDIRECT_NTH (vsscanf,
const char *__restrict __format,
__gnuc_va_list __arg), __isoc99_vsscanf)
__attribute__ ((__format__ (__scanf__, 2, 0)));
-# else
+# elif !defined __REDIRECT
extern int __isoc99_vfscanf (FILE *__restrict __s,
const char *__restrict __format,
__gnuc_va_list __arg) __wur;
diff --git a/libio/vscanf.c b/libio/vscanf.c
index a3e2dd43f2..db89259ccb 100644
--- a/libio/vscanf.c
+++ b/libio/vscanf.c
@@ -24,6 +24,11 @@
This exception applies to code released by its copyright holders
in files containing the exception. */
+/* This file defines one of the deprecated scanf variants. */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
#include "libioP.h"
#include "stdio.h"
diff --git a/misc/mntent_r.c b/misc/mntent_r.c
index 7a82658654..4e1a56620a 100644
--- a/misc/mntent_r.c
+++ b/misc/mntent_r.c
@@ -26,6 +26,10 @@
#define flockfile(s) _IO_flockfile (s)
#define funlockfile(s) _IO_funlockfile (s)
+/* __REDIRECT isn't transitive. */
+#undef sscanf
+#define sscanf __isoc99_sscanf
+
#undef __setmntent
#undef __endmntent
#undef __getmntent_r
diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index 8978b3fb1f..85348a6077 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -65,6 +65,8 @@ tests := tstscanf test_rdwr test-popen tstgetln test-fseek \
tst-vfprintf-mbs-prec \
tst-scanf-round \
tst-renameat2 tst-bz11319 tst-bz11319-fortify2 \
+ scanf14a scanf16a \
+
test-srcs = tst-unbputc tst-printf tst-printfsz-islongdouble
@@ -146,13 +148,11 @@ CFLAGS-isoc99_scanf.c += -fexceptions
CFLAGS-errlist.c += $(fno-unit-at-a-time)
CFLAGS-siglist.c += $(fno-unit-at-a-time)
-# The following is a hack since we must compile scanf1{5,7}.c without any
-# GNU extension. The latter are needed, though, when internal headers
-# are used. So made sure we see the installed headers first.
-CFLAGS-scanf15.c += -I../libio -I../stdlib -I../wcsmbs -I../time -I../string \
- -I../wctype
-CFLAGS-scanf17.c += -I../libio -I../stdlib -I../wcsmbs -I../time -I../string \
- -I../wctype
+# scanf14a.c and scanf16a.c test a deprecated extension which is no
+# longer visible under most conformance levels; see the source files
+# for more detail.
+CFLAGS-scanf14a.c += -std=gnu89
+CFLAGS-scanf16a.c += -std=gnu89
CFLAGS-bug3.c += -DOBJPFX=\"$(objpfx)\"
CFLAGS-bug4.c += -DOBJPFX=\"$(objpfx)\"
diff --git a/stdio-common/bug21.c b/stdio-common/bug21.c
index 7a8c6a3542..1f06c0dab4 100644
--- a/stdio-common/bug21.c
+++ b/stdio-common/bug21.c
@@ -1,5 +1,4 @@
#include <stdio.h>
-#include <libc-diag.h>
static int
do_test (void)
@@ -7,15 +6,7 @@ do_test (void)
static const char buf[] = " ";
char *str;
- /* GCC in C99 mode treats %a as the C99 format expecting float *,
- but glibc with _GNU_SOURCE treats %as as the GNU allocation
- extension, so resulting in "warning: format '%a' expects argument
- of type 'float *', but argument 3 has type 'char **'". This
- applies to the other %as, %aS and %a[] formats below as well. */
- DIAG_PUSH_NEEDS_COMMENT;
- DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
- int r = sscanf (buf, "%as", &str);
- DIAG_POP_NEEDS_COMMENT;
+ int r = sscanf (buf, "%ms", &str);
printf ("%d %p\n", r, str);
return r != -1 || str != NULL;
diff --git a/stdio-common/fscanf.c b/stdio-common/fscanf.c
index b60a2a3b81..9f2a7cdef9 100644
--- a/stdio-common/fscanf.c
+++ b/stdio-common/fscanf.c
@@ -15,6 +15,11 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+/* This file defines one of the deprecated scanf variants. */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
#include <libioP.h>
#include <stdarg.h>
#include <stdio.h>
diff --git a/stdio-common/isoc99_sscanf.c b/stdio-common/isoc99_sscanf.c
index c9e5103b81..7edf5307ee 100644
--- a/stdio-common/isoc99_sscanf.c
+++ b/stdio-common/isoc99_sscanf.c
@@ -33,3 +33,4 @@ __isoc99_sscanf (const char *s, const char *format, ...)
return done;
}
+libc_hidden_def (__isoc99_sscanf)
diff --git a/stdio-common/scanf.c b/stdio-common/scanf.c
index de38d70353..ebcbb070a8 100644
--- a/stdio-common/scanf.c
+++ b/stdio-common/scanf.c
@@ -15,6 +15,11 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+/* This file defines one of the deprecated scanf variants. */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
#include <stdarg.h>
#include <stdio.h>
diff --git a/stdio-common/scanf14.c b/stdio-common/scanf14.c
index 2bcd9c9893..22e5f08341 100644
--- a/stdio-common/scanf14.c
+++ b/stdio-common/scanf14.c
@@ -2,7 +2,10 @@
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
-#include <libc-diag.h>
+
+#if __GLIBC_USE_DEPRECATED_SCANF
+# error "This file should not be compiled with deprecated scanf"
+#endif
#define FAIL() \
do { \
@@ -24,14 +27,7 @@ main (void)
FAIL ();
else if (f != 0.25 || memcmp (c, "s x", 3) != 0)
FAIL ();
- /* GCC in C99 mode treats %a as the C99 format expecting float *,
- but glibc with _GNU_SOURCE treats %as as the GNU allocation
- extension, so resulting in "warning: format '%a' expects argument
- of type 'float *', but argument 3 has type 'char **'". This
- applies to the other %as, %aS and %a[] formats below as well. */
- DIAG_PUSH_NEEDS_COMMENT;
- DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
- if (sscanf (" 1.25s x", "%as%2c", &sp, c) != 2)
+ if (sscanf (" 1.25s x", "%ms%2c", &sp, c) != 2)
FAIL ();
else
{
@@ -40,15 +36,11 @@ main (void)
memset (sp, 'x', sizeof "1.25s");
free (sp);
}
- DIAG_POP_NEEDS_COMMENT;
if (sscanf (" 2.25s x", "%las%2c", &d, c) != 2)
FAIL ();
else if (d != 2.25 || memcmp (c, " x", 2) != 0)
FAIL ();
- /* See explanation above. */
- DIAG_PUSH_NEEDS_COMMENT;
- DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
- if (sscanf (" 3.25S x", "%4aS%3c", &lsp, c) != 2)
+ if (sscanf (" 3.25S x", "%4mS%3c", &lsp, c) != 2)
FAIL ();
else
{
@@ -57,7 +49,7 @@ main (void)
memset (lsp, 'x', sizeof L"3.25");
free (lsp);
}
- if (sscanf ("4.25[0-9.] x", "%a[0-9.]%8c", &sp, c) != 2)
+ if (sscanf ("4.25[0-9.] x", "%m[0-9.]%8c", &sp, c) != 2)
FAIL ();
else
{
@@ -66,7 +58,6 @@ main (void)
memset (sp, 'x', sizeof "4.25");
free (sp);
}
- DIAG_POP_NEEDS_COMMENT;
if (sscanf ("5.25[0-9.] x", "%la[0-9.]%2c", &d, c) != 2)
FAIL ();
else if (d != 5.25 || memcmp (c, " x", 2) != 0)
@@ -95,10 +86,7 @@ main (void)
FAIL ();
if (fseek (fp, 0, SEEK_SET) != 0)
FAIL ();
- /* See explanation above. */
- DIAG_PUSH_NEEDS_COMMENT;
- DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
- if (fscanf (fp, "%as%2c", &sp, c) != 2)
+ if (fscanf (fp, "%ms%2c", &sp, c) != 2)
FAIL ();
else
{
@@ -107,16 +95,12 @@ main (void)
memset (sp, 'x', sizeof "1.25s");
free (sp);
}
- DIAG_POP_NEEDS_COMMENT;
if (freopen (fname, "r", stdin) == NULL)
FAIL ();
else
{
- /* See explanation above. */
- DIAG_PUSH_NEEDS_COMMENT;
- DIAG_IGNORE_NEEDS_COMMENT (4.9, "-Wformat");
- if (scanf ("%as%2c", &sp, c) != 2)
+ if (scanf ("%ms%2c", &sp, c) != 2)
FAIL ();
else
{
@@ -125,7 +109,6 @@ main (void)
memset (sp, 'x', sizeof "1.25s");
free (sp);
}
- DIAG_POP_NEEDS_COMMENT;
}
fclose (fp);
diff --git a/stdio-common/scanf14a.c b/stdio-common/scanf14a.c
new file mode 100644
index 0000000000..34099b8fe3
--- /dev/null
+++ b/stdio-common/scanf14a.c
@@ -0,0 +1,126 @@
+/* This test exercises the deprecated GNU %as, %aS, and %a[...] scanf
+ modifiers, which are not available to programs compiled as C99
+ anymore; therefore, this file is compiled with -std=gnu89 and C99
+ syntax must not be used. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <wchar.h>
+
+#if !__GLIBC_USE_DEPRECATED_SCANF
+# error "This file should be compiled with deprecated scanf"
+#endif
+
+
+#define FAIL() \
+ do { \
+ result = 1; \
+ printf ("test at line %d failed\n", __LINE__); \
+ } while (0)
+
+int
+main (void)
+{
+ wchar_t *lsp;
+ char *sp;
+ float f;
+ double d;
+ char c[8];
+ int result = 0;
+
+ if (sscanf (" 0.25s x", "%e%3c", &f, c) != 2)
+ FAIL ();
+ else if (f != 0.25 || memcmp (c, "s x", 3) != 0)
+ FAIL ();
+ if (sscanf (" 1.25s x", "%as%2c", &sp, c) != 2)
+ FAIL ();
+ else
+ {
+ if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+ FAIL ();
+ memset (sp, 'x', sizeof "1.25s");
+ free (sp);
+ }
+ if (sscanf (" 2.25s x", "%las%2c", &d, c) != 2)
+ FAIL ();
+ else if (d != 2.25 || memcmp (c, " x", 2) != 0)
+ FAIL ();
+ if (sscanf (" 3.25S x", "%4aS%3c", &lsp, c) != 2)
+ FAIL ();
+ else
+ {
+ if (wcscmp (lsp, L"3.25") != 0 || memcmp (c, "S x", 3) != 0)
+ FAIL ();
+ memset (lsp, 'x', sizeof L"3.25");
+ free (lsp);
+ }
+ if (sscanf ("4.25[0-9.] x", "%a[0-9.]%8c", &sp, c) != 2)
+ FAIL ();
+ else
+ {
+ if (strcmp (sp, "4.25") != 0 || memcmp (c, "[0-9.] x", 8) != 0)
+ FAIL ();
+ memset (sp, 'x', sizeof "4.25");
+ free (sp);
+ }
+ if (sscanf ("5.25[0-9.] x", "%la[0-9.]%2c", &d, c) != 2)
+ FAIL ();
+ else if (d != 5.25 || memcmp (c, " x", 2) != 0)
+ FAIL ();
+
+ const char *tmpdir = getenv ("TMPDIR");
+ if (tmpdir == NULL || tmpdir[0] == '\0')
+ tmpdir = "/tmp";
+
+ char fname[strlen (tmpdir) + sizeof "/tst-scanf14.XXXXXX"];
+ sprintf (fname, "%s/tst-scanf14.XXXXXX", tmpdir);
+ if (fname == NULL)
+ FAIL ();
+
+ /* Create a temporary file. */
+ int fd = mkstemp (fname);
+ if (fd == -1)
+ FAIL ();
+
+ FILE *fp = fdopen (fd, "w+");
+ if (fp == NULL)
+ FAIL ();
+ else
+ {
+ if (fputs (" 1.25s x", fp) == EOF)
+ FAIL ();
+ if (fseek (fp, 0, SEEK_SET) != 0)
+ FAIL ();
+ if (fscanf (fp, "%as%2c", &sp, c) != 2)
+ FAIL ();
+ else
+ {
+ if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+ FAIL ();
+ memset (sp, 'x', sizeof "1.25s");
+ free (sp);
+ }
+
+ if (freopen (fname, "r", stdin) == NULL)
+ FAIL ();
+ else
+ {
+ if (scanf ("%as%2c", &sp, c) != 2)
+ FAIL ();
+ else
+ {
+ if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+ FAIL ();
+ memset (sp, 'x', sizeof "1.25s");
+ free (sp);
+ }
+ }
+
+ fclose (fp);
+ }
+
+ remove (fname);
+
+ return result;
+}
diff --git a/stdio-common/scanf15.c b/stdio-common/scanf15.c
index a3ab15dea2..142e215ad3 100644
--- a/stdio-common/scanf15.c
+++ b/stdio-common/scanf15.c
@@ -1,18 +1,12 @@
-#undef _GNU_SOURCE
-#define _XOPEN_SOURCE 600
-#undef _LIBC
-#undef _IO_MTSAFE_IO
-/* The following macro definitions are a hack. They word around disabling
- the GNU extension while still using a few internal headers. */
-#define u_char unsigned char
-#define u_short unsigned short
-#define u_int unsigned int
-#define u_long unsigned long
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
+#if __GLIBC_USE_DEPRECATED_SCANF
+# error "This file should not be compiled with deprecated scanf"
+#endif
+
#define FAIL() \
do { \
result = 1; \
diff --git a/stdio-common/scanf16.c b/stdio-common/scanf16.c
index 3e3cb417f2..db640e2e9c 100644
--- a/stdio-common/scanf16.c
+++ b/stdio-common/scanf16.c
@@ -4,13 +4,17 @@
#include <string.h>
#include <wchar.h>
+#if __GLIBC_USE_DEPRECATED_SCANF
+# error "This file should not be compiled with deprecated scanf"
+#endif
+
#define FAIL() \
do { \
result = 1; \
printf ("test at line %d failed\n", __LINE__); \
} while (0)
-static int
+static int __attribute__ ((format (scanf, 2, 3)))
xsscanf (const char *str, const char *fmt, ...)
{
va_list ap;
@@ -20,7 +24,7 @@ xsscanf (const char *str, const char *fmt, ...)
return ret;
}
-static int
+static int __attribute__ ((format (scanf, 1, 2)))
xscanf (const char *fmt, ...)
{
va_list ap;
@@ -30,7 +34,7 @@ xscanf (const char *fmt, ...)
return ret;
}
-static int
+static int __attribute__ ((format (scanf, 2, 3)))
xfscanf (FILE *f, const char *fmt, ...)
{
va_list ap;
@@ -54,7 +58,7 @@ main (void)
FAIL ();
else if (f != 0.25 || memcmp (c, "s x", 3) != 0)
FAIL ();
- if (xsscanf (" 1.25s x", "%as%2c", &sp, c) != 2)
+ if (xsscanf (" 1.25s x", "%ms%2c", &sp, c) != 2)
FAIL ();
else
{
@@ -67,7 +71,7 @@ main (void)
FAIL ();
else if (d != 2.25 || memcmp (c, " x", 2) != 0)
FAIL ();
- if (xsscanf (" 3.25S x", "%4aS%3c", &lsp, c) != 2)
+ if (xsscanf (" 3.25S x", "%4mS%3c", &lsp, c) != 2)
FAIL ();
else
{
@@ -76,7 +80,7 @@ main (void)
memset (lsp, 'x', sizeof L"3.25");
free (lsp);
}
- if (xsscanf ("4.25[0-9.] x", "%a[0-9.]%8c", &sp, c) != 2)
+ if (xsscanf ("4.25[0-9.] x", "%m[0-9.]%8c", &sp, c) != 2)
FAIL ();
else
{
@@ -113,7 +117,7 @@ main (void)
FAIL ();
if (fseek (fp, 0, SEEK_SET) != 0)
FAIL ();
- if (xfscanf (fp, "%as%2c", &sp, c) != 2)
+ if (xfscanf (fp, "%ms%2c", &sp, c) != 2)
FAIL ();
else
{
@@ -127,7 +131,7 @@ main (void)
FAIL ();
else
{
- if (xscanf ("%as%2c", &sp, c) != 2)
+ if (xscanf ("%ms%2c", &sp, c) != 2)
FAIL ();
else
{
diff --git a/stdio-common/scanf16a.c b/stdio-common/scanf16a.c
new file mode 100644
index 0000000000..684eeb08f4
--- /dev/null
+++ b/stdio-common/scanf16a.c
@@ -0,0 +1,156 @@
+/* This test exercises the deprecated GNU %as, %aS, and %a[...] scanf
+ modifiers, which are not available to programs compiled as C99
+ anymore; therefore, this file is compiled with -std=gnu89 and C99
+ syntax must not be used. */
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <wchar.h>
+
+#if !__GLIBC_USE_DEPRECATED_SCANF
+# error "This file should be compiled with deprecated scanf"
+#endif
+
+#define FAIL() \
+ do { \
+ result = 1; \
+ printf ("test at line %d failed\n", __LINE__); \
+ } while (0)
+
+static int __attribute__ ((format (scanf, 2, 3)))
+xsscanf (const char *str, const char *fmt, ...)
+{
+ va_list ap;
+ va_start (ap, fmt);
+ int ret = vsscanf (str, fmt, ap);
+ va_end (ap);
+ return ret;
+}
+
+static int __attribute__ ((format (scanf, 1, 2)))
+xscanf (const char *fmt, ...)
+{
+ va_list ap;
+ va_start (ap, fmt);
+ int ret = vscanf (fmt, ap);
+ va_end (ap);
+ return ret;
+}
+
+static int __attribute__ ((format (scanf, 2, 3)))
+xfscanf (FILE *f, const char *fmt, ...)
+{
+ va_list ap;
+ va_start (ap, fmt);
+ int ret = vfscanf (f, fmt, ap);
+ va_end (ap);
+ return ret;
+}
+
+int
+main (void)
+{
+ wchar_t *lsp;
+ char *sp;
+ float f;
+ double d;
+ char c[8];
+ int result = 0;
+
+ if (xsscanf (" 0.25s x", "%e%3c", &f, c) != 2)
+ FAIL ();
+ else if (f != 0.25 || memcmp (c, "s x", 3) != 0)
+ FAIL ();
+ if (xsscanf (" 1.25s x", "%as%2c", &sp, c) != 2)
+ FAIL ();
+ else
+ {
+ if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+ FAIL ();
+ memset (sp, 'x', sizeof "1.25s");
+ free (sp);
+ }
+ if (xsscanf (" 2.25s x", "%las%2c", &d, c) != 2)
+ FAIL ();
+ else if (d != 2.25 || memcmp (c, " x", 2) != 0)
+ FAIL ();
+ if (xsscanf (" 3.25S x", "%4aS%3c", &lsp, c) != 2)
+ FAIL ();
+ else
+ {
+ if (wcscmp (lsp, L"3.25") != 0 || memcmp (c, "S x", 3) != 0)
+ FAIL ();
+ memset (lsp, 'x', sizeof L"3.25");
+ free (lsp);
+ }
+ if (xsscanf ("4.25[0-9.] x", "%a[0-9.]%8c", &sp, c) != 2)
+ FAIL ();
+ else
+ {
+ if (strcmp (sp, "4.25") != 0 || memcmp (c, "[0-9.] x", 8) != 0)
+ FAIL ();
+ memset (sp, 'x', sizeof "4.25");
+ free (sp);
+ }
+ if (xsscanf ("5.25[0-9.] x", "%la[0-9.]%2c", &d, c) != 2)
+ FAIL ();
+ else if (d != 5.25 || memcmp (c, " x", 2) != 0)
+ FAIL ();
+
+ const char *tmpdir = getenv ("TMPDIR");
+ if (tmpdir == NULL || tmpdir[0] == '\0')
+ tmpdir = "/tmp";
+
+ char fname[strlen (tmpdir) + sizeof "/tst-scanf16.XXXXXX"];
+ sprintf (fname, "%s/tst-scanf16.XXXXXX", tmpdir);
+ if (fname == NULL)
+ FAIL ();
+
+ /* Create a temporary file. */
+ int fd = mkstemp (fname);
+ if (fd == -1)
+ FAIL ();
+
+ FILE *fp = fdopen (fd, "w+");
+ if (fp == NULL)
+ FAIL ();
+ else
+ {
+ if (fputs (" 1.25s x", fp) == EOF)
+ FAIL ();
+ if (fseek (fp, 0, SEEK_SET) != 0)
+ FAIL ();
+ if (xfscanf (fp, "%as%2c", &sp, c) != 2)
+ FAIL ();
+ else
+ {
+ if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+ FAIL ();
+ memset (sp, 'x', sizeof "1.25s");
+ free (sp);
+ }
+
+ if (freopen (fname, "r", stdin) == NULL)
+ FAIL ();
+ else
+ {
+ if (xscanf ("%as%2c", &sp, c) != 2)
+ FAIL ();
+ else
+ {
+ if (strcmp (sp, "1.25s") != 0 || memcmp (c, " x", 2) != 0)
+ FAIL ();
+ memset (sp, 'x', sizeof "1.25s");
+ free (sp);
+ }
+ }
+
+ fclose (fp);
+ }
+
+ remove (fname);
+
+ return result;
+}
diff --git a/stdio-common/scanf17.c b/stdio-common/scanf17.c
index b6c0e63ab0..5a0ae42686 100644
--- a/stdio-common/scanf17.c
+++ b/stdio-common/scanf17.c
@@ -1,19 +1,13 @@
-#undef _GNU_SOURCE
-#define _XOPEN_SOURCE 600
-#undef _LIBC
-#undef _IO_MTSAFE_IO
-/* The following macro definitions are a hack. They word around disabling
- the GNU extension while still using a few internal headers. */
-#define u_char unsigned char
-#define u_short unsigned short
-#define u_int unsigned int
-#define u_long unsigned long
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
+#if __GLIBC_USE_DEPRECATED_SCANF
+# error "This file should not be compiled with deprecated scanf"
+#endif
+
#define FAIL() \
do { \
result = 1; \
diff --git a/stdio-common/sscanf.c b/stdio-common/sscanf.c
index e25e9c27a5..1c8c58bbe9 100644
--- a/stdio-common/sscanf.c
+++ b/stdio-common/sscanf.c
@@ -15,6 +15,11 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+/* This file defines one of the deprecated scanf variants. */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
#include <stdarg.h>
#include <libio/strfile.h>
@@ -34,6 +39,5 @@ __sscanf (const char *s, const char *format, ...)
return done;
}
-ldbl_hidden_def (__sscanf, sscanf)
ldbl_strong_alias (__sscanf, sscanf)
ldbl_strong_alias (__sscanf, _IO_sscanf)
diff --git a/stdio-common/vfscanf.c b/stdio-common/vfscanf.c
index 5eedca8340..b9df35e73b 100644
--- a/stdio-common/vfscanf.c
+++ b/stdio-common/vfscanf.c
@@ -15,6 +15,11 @@
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
+/* This file defines one of the deprecated scanf variants. */
+#include <features.h>
+#undef __GLIBC_USE_DEPRECATED_SCANF
+#define __GLIBC_USE_DEPRECATED_SCANF 1
+
#include <libioP.h>
int
diff --git a/time/tzset.c b/time/tzset.c
index 834cc3ccec..3807b2830b 100644
--- a/time/tzset.c
+++ b/time/tzset.c
@@ -26,6 +26,10 @@
#include <timezone/tzfile.h>
+/* __REDIRECT isn't transitive. */
+#undef sscanf
+#define sscanf __isoc99_sscanf
+
#define SECSPERDAY ((__time64_t) 86400)
char *__tzname[2] = { (char *) "GMT", (char *) "GMT" };
--
2.20.0.rc1
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Use C99-compliant scanf under _GNU_SOURCE with C99/C++11 and higher.
2018-12-17 16:53 [PATCH] Use C99-compliant scanf under _GNU_SOURCE with C99/C++11 and higher Zack Weinberg
@ 2018-12-17 16:59 ` Andreas Schwab
2018-12-17 17:04 ` Zack Weinberg
2018-12-17 17:01 ` Florian Weimer
1 sibling, 1 reply; 6+ messages in thread
From: Andreas Schwab @ 2018-12-17 16:59 UTC (permalink / raw)
To: Zack Weinberg; +Cc: libc-alpha, adhemerval.zanella
On Dez 17 2018, Zack Weinberg <zackw@panix.com> wrote:
> On a related note, the interaction of the C99/not-C99 scanf redirect
> with the __LDBL_COMPAT scanf redirect was complicated, confusing,
> and possibly wrong. The __ldbl_is_dbl cleanup (thanks to Gabriel
> Gomes for finishing that for me) has made it less complicated, but
> I'm still not 100% sure it's correct, and I do not have access to
> physical hardware for which __LDBL_COMPAT is relevant, so my ability
> to test it is limited. Careful review (you'll want to read all of
> libio/bits/stdio-ldbl.h to understand what's going on, not just
> the diff) and maybe even some volunteer testing would be appreciated.
I have started a test build of your branch in
<https://build.opensuse.org/package/show/home:Andreas_Schwab:glibc:test/glibc>.
[ 881s] In file included from <command-line>:
[ 881s] ../sysdeps/ieee754/ldbl-opt/nldbl-sscanf.c:17:23: error: '_IO_sscanf' aliased to undefined symbol 'sscanf'
[ 881s] strong_alias (sscanf, _IO_sscanf)
[ 881s] ^~~~~~~~~~
[ 881s] ./../include/libc-symbols.h:140:26: note: in definition of macro '_strong_alias'
[ 881s] extern __typeof (name) aliasname __attribute__ ((alias (#name))) \
[ 881s] ^~~~~~~~~
[ 881s] ../sysdeps/ieee754/ldbl-opt/nldbl-sscanf.c:17:1: note: in expansion of macro 'strong_alias'
[ 881s] strong_alias (sscanf, _IO_sscanf)
[ 881s] ^~~~~~~~~~~~
[ 881s] make[2]: *** [/home/abuild/rpmbuild/BUILD/glibc-2.28.9000.401.ge4bbeb76ee/cc-base/sysd-rules:831: /home/abuild/rpmbuild/BUILD/glibc-2.28.9000.401.ge4bbeb76ee/cc-base/math/nldbl-sscanf.oS] Error 1
Andreas.
--
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Use C99-compliant scanf under _GNU_SOURCE with C99/C++11 and higher.
2018-12-17 16:53 [PATCH] Use C99-compliant scanf under _GNU_SOURCE with C99/C++11 and higher Zack Weinberg
2018-12-17 16:59 ` Andreas Schwab
@ 2018-12-17 17:01 ` Florian Weimer
2018-12-17 17:22 ` Zack Weinberg
1 sibling, 1 reply; 6+ messages in thread
From: Florian Weimer @ 2018-12-17 17:01 UTC (permalink / raw)
To: Zack Weinberg; +Cc: libc-alpha, adhemerval.zanella
* Zack Weinberg:
> +* An archaic GNU extension to scanf, under which '%as', '%aS', and '%a[...]'
> + meant to scan a string and allocate space for it with malloc, is now
> + restricted to programs compiled in C89 or C++98 mode with _GNU_SOURCE
> + defined. This extension conflicts with C99's use of '%a' to scan a
> + hexadecimal floating-point number, which is now available to programs
> + compiled as C99 or C++11 or higher, regardless of _GNU_SOURCE.
> +
> + POSIX.1-2008 includes the feature of allocating a buffer for string input
> + with malloc, using the modifier letter 'm' instead. Programs using
> + '%as', '%aS', or '%a[...]' with the old GNU meaning should change to
> + '%ms', '%mS', or '%m[...]' respectively. Programs that wish to use the
> + C99 '%a' no longer need to avoid _GNU_SOURCE.
> +
> + GCC's -Wformat warnings can detect most uses of this extension, as long
> + as all functions that call vscanf, vfscanf, or vsscanf are annotated with
> + __attribute__ ((format (scanf, ...))).
What's the state of GCC warnings? Does GCC already anticipate this
change?
Thanks,
Florian
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Use C99-compliant scanf under _GNU_SOURCE with C99/C++11 and higher.
2018-12-17 16:59 ` Andreas Schwab
@ 2018-12-17 17:04 ` Zack Weinberg
0 siblings, 0 replies; 6+ messages in thread
From: Zack Weinberg @ 2018-12-17 17:04 UTC (permalink / raw)
To: Andreas Schwab; +Cc: GNU C Library
On Mon, Dec 17, 2018 at 11:56 AM Andreas Schwab <schwab@suse.de> wrote:
> On Dez 17 2018, Zack Weinberg <zackw@panix.com> wrote:
>
> > On a related note, the interaction of the C99/not-C99 scanf redirect
> > with the __LDBL_COMPAT scanf redirect was complicated, confusing,
> > and possibly wrong. The __ldbl_is_dbl cleanup (thanks to Gabriel
> > Gomes for finishing that for me) has made it less complicated, but
> > I'm still not 100% sure it's correct, and I do not have access to
> > physical hardware for which __LDBL_COMPAT is relevant, so my ability
> > to test it is limited. Careful review (you'll want to read all of
> > libio/bits/stdio-ldbl.h to understand what's going on, not just
> > the diff) and maybe even some volunteer testing would be appreciated.
>
> I have started a test build of your branch in
> <https://build.opensuse.org/package/show/home:Andreas_Schwab:glibc:test/glibc>.
>
> [ 881s] In file included from <command-line>:
> [ 881s] ../sysdeps/ieee754/ldbl-opt/nldbl-sscanf.c:17:23: error: '_IO_sscanf' aliased to undefined symbol 'sscanf'
> [ 881s] strong_alias (sscanf, _IO_sscanf)
> [ 881s] ^~~~~~~~~~
Argh. I will throw the patch at my local build-many-glibcs setup and
hopefully that will let me reproduce this problem and fix it. Thanks.
zw
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Use C99-compliant scanf under _GNU_SOURCE with C99/C++11 and higher.
2018-12-17 17:01 ` Florian Weimer
@ 2018-12-17 17:22 ` Zack Weinberg
2018-12-17 17:34 ` Florian Weimer
0 siblings, 1 reply; 6+ messages in thread
From: Zack Weinberg @ 2018-12-17 17:22 UTC (permalink / raw)
To: Florian Weimer; +Cc: GNU C Library, Adhemerval Zanella
On Mon, Dec 17, 2018 at 12:01 PM Florian Weimer <fweimer@redhat.com> wrote:
> * Zack Weinberg:
> > +
> > + GCC's -Wformat warnings can detect most uses of this extension, as long
> > + as all functions that call vscanf, vfscanf, or vsscanf are annotated with
> > + __attribute__ ((format (scanf, ...))).
>
> What's the state of GCC warnings? Does GCC already anticipate this
> change?
Yes, that's what I meant. Current versions of GCC, in -std=[c|gnu]99
mode, already diagnose use of `%as` in the old GNU sense, regardless
of _GNU_SOURCE.
$ cat test.c
#include <stdio.h>
int main(void)
{
char *foo;
scanf("%as", &foo);
printf("%s", foo);
return 0;
}
$ gcc --version
gcc (Debian 8.2.0-12) 8.2.0
Copyright (C) 2018 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ gcc -std=gnu89 -D_GNU_SOURCE -c -Wall test.c
[no warnings]
$ gcc -std=gnu99 -D_GNU_SOURCE -c -Wall test.c
test.c: In function ‘main’:
test.c:6:11: warning: format ‘%a’ expects argument of type ‘float *’,
but argument 2 has type ‘char **’ [-Wformat=]
scanf("%as", &foo);
~^ ~~~~
I don't know how long this has been true.
zw
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] Use C99-compliant scanf under _GNU_SOURCE with C99/C++11 and higher.
2018-12-17 17:22 ` Zack Weinberg
@ 2018-12-17 17:34 ` Florian Weimer
0 siblings, 0 replies; 6+ messages in thread
From: Florian Weimer @ 2018-12-17 17:34 UTC (permalink / raw)
To: Zack Weinberg; +Cc: GNU C Library, Adhemerval Zanella
* Zack Weinberg:
> On Mon, Dec 17, 2018 at 12:01 PM Florian Weimer <fweimer@redhat.com> wrote:
>> * Zack Weinberg:
>> > +
>> > + GCC's -Wformat warnings can detect most uses of this extension, as long
>> > + as all functions that call vscanf, vfscanf, or vsscanf are annotated with
>> > + __attribute__ ((format (scanf, ...))).
>>
>> What's the state of GCC warnings? Does GCC already anticipate this
>> change?
>
> Yes, that's what I meant. Current versions of GCC, in -std=[c|gnu]99
> mode, already diagnose use of `%as` in the old GNU sense, regardless
> of _GNU_SOURCE.
Looks like this behavior goes back to GCC 4.1 at least. Interesting.
Of course, what changed over time is the default compilation mode.
So I think the NEWS text is okay.
Thanks,
Florian
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-12-17 17:32 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-12-17 16:53 [PATCH] Use C99-compliant scanf under _GNU_SOURCE with C99/C++11 and higher Zack Weinberg
2018-12-17 16:59 ` Andreas Schwab
2018-12-17 17:04 ` Zack Weinberg
2018-12-17 17:01 ` Florian Weimer
2018-12-17 17:22 ` Zack Weinberg
2018-12-17 17:34 ` Florian Weimer
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