Re: [PATCH] libssp: Fix gets-chk.c compilation on Solaris

[Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>]

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Hi Jakub,

sorry for dropping the ball on this.

> On Mon, Dec 04, 2023 at 11:42:09AM +0100, Rainer Orth wrote:
>> The recent warning patches broke the libssp build on Solaris:
>> 
>> /vol/gcc/src/hg/master/local/libssp/gets-chk.c: In function '__gets_chk':
>> /vol/gcc/src/hg/master/local/libssp/gets-chk.c:67:12: error: implicit
>> declaration of function 'gets'; did you mean 'getw'?
>> [-Wimplicit-function-declaration]
>>    67 |     return gets (s);
>>       |            ^~~~
>>       |            getw 
>> /vol/gcc/src/hg/master/local/libssp/gets-chk.c:67:12: error: returning
>> 'int' from a function with return type 'char *' makes pointer from
>> integer without a cast [-Wint-conversion]
>>    67 |     return gets (s);
>>       |            ^~~~~~~~
>> /vol/gcc/src/hg/master/local/libssp/gets-chk.c:74:12: error: returning
>> 'int' from a function with return type 'char *' makes pointer from
>> integer without a cast [-Wint-conversion]
>>    74 |     return gets (s);
>>       |            ^~~~~~~~
>> 
>> The guard around the gets declaration in gets-chk.c is
>> 
>> #if !(!defined __USE_ISOC11                             \
>>       || (defined __cplusplus && __cplusplus <= 201103L))
>> extern char *gets (char *);
>> #endif
>> 
>> __USE_ISOC11 is a glibc-only thing, while Solaris <iso/stdio_iso.h>
>> declares gets like
>> 
>> #if __STDC_VERSION__ < 201112L && __cplusplus < 201402L
>> extern char     *gets(char *) __ATTR_DEPRECATED;
>> #endif
>> 
>> If one needs to check __USE_ISO11 at all, one certainly needs to check
>> __STDC_VERSION__ to avoid breaking every non-glibc target.  Besides, I
>> don't see what's the use of checking __cplusplus when compiling a C-only
>> source file.  On top of all that, the double negation makes the guard
>> unnecessarily hard to understand.
>> 
>> I really don't know if it's useful/appropriate to check __USE_ISOC11 and
>> __cplusplus here at all; still I've left both for now.
>> 
>> Here's what I've used to complete the Solaris bootstrap.
>> 
>> Tested on i386-pc-solaris2.11, sparc-sun-solaris2.11,
>> x86_64-pc-linux-gnu, and x86_64-apple-darwin23.1.0.
>> 
>> -- 
>> -----------------------------------------------------------------------------
>> Rainer Orth, Center for Biotechnology, Bielefeld University
>> 
>> 
>> 2023-12-03  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>
>> 
>> 	libssp:
>> 	* gets-chk.c (gets): Avoid double negation.
>> 	Also check __STDC_VERSION__ >= 201112L.
>> 
>
>> # HG changeset patch
>> # Parent  334015ab01f6c0e5af821c1e9bc83b8677cc0bfb
>> libssp: Fix gets-chk.c compilation on Solaris
>> 
>> diff --git a/libssp/gets-chk.c b/libssp/gets-chk.c
>> --- a/libssp/gets-chk.c
>> +++ b/libssp/gets-chk.c
>> @@ -51,8 +51,9 @@ see the files COPYING3 and COPYING.RUNTI
>>  # include <string.h>
>>  #endif
>>  
>> -#if !(!defined __USE_ISOC11				\
>> -      || (defined __cplusplus && __cplusplus <= 201103L))
>> +#if (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L)	\
>> +     || !defined __USE_ISOC11					\
>> +     || (defined __cplusplus && __cplusplus >= 201402L)
>
> The above isn't equivalent.  Avoiding double negation would mean
> #if (defined __USE_ISOC11				\
>      && !(defined __cplusplus && __cplusplus <= 201103L))
> or
> #if (defined __USE_ISOC11				\
>      && (!defined __cplusplus || __cplusplus > 201103L))
> No?
> __USE_ISOC11 is defined as
> /* This is to enable the ISO C11 extension.  */
> #if (defined _ISOC11_SOURCE || defined _ISOC2X_SOURCE \
>      || (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L))
> # define __USE_ISOC11   1
> #endif
> where _ISOC11_SOURCE or _ISOC2X_SOURCE are defined whenever _GNU_SOURCE
> is or when user defines them, or __USE_ISOC11 is also defined for
> if __cplusplus >= 201703L.
>
> Obviously, if you add that
>   (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L)
> it will mean it will be prototyped always (as I think we compile it without
> any -std= flags).
>
> What about using what we had for glibc (or even better, expect gets
> to be declared for glibc < 2.16) and use what you add for other libraries?
> The file is written and compiled as C, so we don't need to bother with C++
> though.
> So
> #if (defined (__GLIBC_PREREQ)						\
>      ? (__GLIBC_PREREQ (2, 16) && defined (__USE_ISOC11))		\
>      : (defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L))
> ?
>
>>  extern char *gets (char *);
>>  #endif

this doesn't even compile on non-glibc targets:

/vol/gcc/src/hg/master/local/libssp/gets-chk.c:55:24: error: missing binary operator before token "("
   55 |      ? (__GLIBC_PREREQ (2, 16) && defined (__USE_ISOC11))               \
      |       

Unless one really wants to go for ugly contortions like

#ifdef __GLIBC_PREREQ
# if __GLIBC_PREREQ (2, 16) && defined (__USE_ISOC11)
#  define NEED_DECL_GETS
# endif
#elif defined __STDC_VERSION__ && __STDC_VERSION__ >= 201112L
#  define NEED_DECL_GETS
#endif
#ifdef NEED_DECL_GETS

I still think it's way easier and more reliable to just use the canonical
autoconf test.

Bootstrapped on i386-pc-solaris2.11, sparc-sun-solaris2.11,
x86_64-pc-linux-gnu, x86_64-apple-darwin23.3.0, and
amd64-pc-freebsd14.0.

Ok for trunk?

	Rainer

-- 
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University


2023-12-07  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	libssp:
	* configure.ac (AC_CHECK_DECLS): Check for gets.
	* configure, config.h.in: Regenerate.
	* gets-chk.c (gets): Guard declaration with !HAVE_DECL_GETS.


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# HG changeset patch
# Parent  334015ab01f6c0e5af821c1e9bc83b8677cc0bfb
libssp: Fix gets-chk.c compilation on Solaris

diffdiff --git a/libssp/configure.ac b/libssp/configure.ac
--- a/libssp/configure.ac
+++ b/libssp/configure.ac
@@ -128,6 +128,7 @@ if test x$gcc_no_link = xyes; then
 else
   AC_CHECK_FUNCS(memmove mempcpy strncpy strncat)
 fi
+AC_CHECK_DECLS([gets])
 
 AC_MSG_CHECKING([whether vsnprintf is usable])
 AC_RUN_IFELSE([AC_LANG_PROGRAM([
diff --git a/libssp/gets-chk.c b/libssp/gets-chk.c
--- a/libssp/gets-chk.c
+++ b/libssp/gets-chk.c
@@ -51,8 +51,7 @@ see the files COPYING3 and COPYING.RUNTI
 # include <string.h>
 #endif
 
-#if !(!defined __USE_ISOC11				\
-      || (defined __cplusplus && __cplusplus <= 201103L))
+#if !HAVE_DECL_GETS
 extern char *gets (char *);
 #endif