[RFC v2] Add [v]aprintf(3)

[Alejandro Colomar <alx@kernel.org>]

Signed-off-by: Alejandro Colomar <alx@kernel.org>
---

Hi!

I've figured out how to add these to the Makefiles.  I'm now having
issues with the aliases, which I don't understand at all.  I more or
less imitated how [v]asprintf(3) are implemented, but obviously did
something wrong.

Would you mind helping with this error?

	In file included from <command-line>:
	./../include/libc-symbols.h:474:33: error: ‘__EI_aprintf’ aliased to undefined symbol ‘__GI_aprintf’
	  474 |   extern thread __typeof (name) __EI_##name \
	      |                                 ^~~~~
	./../include/libc-symbols.h:470:3: note: in expansion of macro ‘__hidden_ver2’
	  470 |   __hidden_ver2 (, local, internal, name)
	      |   ^~~~~~~~~~~~~
	./../include/libc-symbols.h:478:41: note: in expansion of macro ‘__hidden_ver1’
	  478 | #  define hidden_def(name)              __hidden_ver1(__GI_##name, name, name);
	      |                                         ^~~~~~~~~~~~~
	./../include/libc-symbols.h:559:32: note: in expansion of macro ‘hidden_def’
	  559 | # define libc_hidden_def(name) hidden_def (name)
	      |                                ^~~~~~~~~~
	../sysdeps/generic/math_ldbl_opt.h:13:38: note: in expansion of macro ‘libc_hidden_def’
	   13 | #define ldbl_hidden_def(local, name) libc_hidden_def (name)
	      |                                      ^~~~~~~~~~~~~~~
	aprintf.c:37:1: note: in expansion of macro ‘ldbl_hidden_def’
	   37 | ldbl_hidden_def (__aprintf, aprintf)
	      | ^~~~~~~~~~~~~~~

Cheers,
Alex

 libio/Makefile         |  3 ++-
 libio/stdio.h          |  8 ++++++++
 libio/vaprintf.c       | 39 +++++++++++++++++++++++++++++++++++++++
 stdio-common/Makefile  |  2 ++
 stdio-common/aprintf.c | 40 ++++++++++++++++++++++++++++++++++++++++
 5 files changed, 91 insertions(+), 1 deletion(-)
 create mode 100644 libio/vaprintf.c
 create mode 100644 stdio-common/aprintf.c

diff --git a/libio/Makefile b/libio/Makefile
index 08e1e0ec..acb578db 100644
--- a/libio/Makefile
+++ b/libio/Makefile
@@ -43,7 +43,7 @@ routines	:=							      \
 									      \
 	clearerr feof ferror fileno fputc freopen fseek getc getchar	      \
 	memstream pclose putc putchar rewind setbuf setlinebuf vasprintf      \
-	iovdprintf vscanf vsnprintf obprintf fcloseall fseeko ftello	      \
+	vaprintf iovdprintf vscanf vsnprintf obprintf fcloseall fseeko ftello \
 	freopen64 fseeko64 ftello64					      \
 									      \
 	__fbufsize __freading __fwriting __freadable __fwritable __flbf	      \
@@ -63,6 +63,7 @@ routines_no_fortify += \
   iovdprintf \
   swprintf \
   vasprintf \
+  vaprintf \
   vsnprintf \
   vswprintf \
   vwprintf \
diff --git a/libio/stdio.h b/libio/stdio.h
index 3bf6a1f6..3db363f1 100644
--- a/libio/stdio.h
+++ b/libio/stdio.h
@@ -410,6 +410,14 @@ extern int __asprintf (char **__restrict __ptr,
 extern int asprintf (char **__restrict __ptr,
 		     const char *__restrict __fmt, ...)
      __THROWNL __attribute__ ((__format__ (__printf__, 2, 3))) __wur;
+
+/* Write formatted output to a string dynamically allocated with `malloc'.  */
+extern char *vaprintf (const char *__restrict __f, __gnuc_va_list __arg)
+     __THROWNL __attribute__ ((__format__ (__printf__, 1, 0)))
+     __attribute_malloc__;
+extern char *aprintf (const char *__restrict __fmt, ...)
+     __THROWNL __attribute__ ((__format__ (__printf__, 1, 2)))
+     __attribute_malloc__;
 #endif
 
 #ifdef __USE_XOPEN2K8
diff --git a/libio/vaprintf.c b/libio/vaprintf.c
new file mode 100644
index 00000000..6789052f
--- /dev/null
+++ b/libio/vaprintf.c
@@ -0,0 +1,39 @@
+/* Copyright (C) 2026 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.
+
+   As a special exception, if you link the code in this file with
+   files compiled with a GNU compiler to produce an executable,
+   that does not cause the resulting executable to be covered by
+   the GNU Lesser General Public License.  This exception does not
+   however invalidate any other reasons why the executable file
+   might be covered by the GNU Lesser General Public License.
+   This exception applies to code released by its copyright holders
+   in files containing the exception.  */
+
+#include <libioP.h>
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdio.h>
+
+char *
+__vaprintf (const char *fmt, va_list args)
+{
+  char *p;
+
+  return __vasprintf_internal (&p, fmt, args, 0) < 0 ? NULL : p;
+}
+ldbl_weak_alias (__vaprintf, vaprintf)
diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index 21094483..ec52c1ea 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -90,6 +90,7 @@ routines := \
   _itoa \
   _itowa \
   asprintf \
+  aprintf \
   ctermid \
   cuserid \
   dprintf \
@@ -178,6 +179,7 @@ routines := \
 # Exclude fortified routines from being built with _FORTIFY_SOURCE
 routines_no_fortify += \
   asprintf \
+  aprintf \
   dprintf \
   fprintf \
   printf \
diff --git a/stdio-common/aprintf.c b/stdio-common/aprintf.c
new file mode 100644
index 00000000..f2d0dbb2
--- /dev/null
+++ b/stdio-common/aprintf.c
@@ -0,0 +1,40 @@
+/* Copyright (C) 2026 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdarg.h>
+#include <libioP.h>
+
+/* Write formatted output from FORMAT to a string which is
+   allocated with malloc.  */
+/* VARARGS1 */
+char *
+___aprintf (const char *fmt, ...)
+{
+  char *p;
+  va_list ap;
+
+  va_start (ap, fmt);
+  if (__vasprintf_internal (&p, fmt, ap, 0) < 0)
+    p = NULL;
+  va_end (ap);
+
+  return p;
+}
+ldbl_hidden_def (__aprintf, aprintf)
+
+ldbl_strong_alias (___aprintf, __aprintf)
+ldbl_weak_alias (___aprintf, aprintf)

Range-diff against v1:
1:  e5defcbd ! 1:  916855e5 libio/: Add [v]aprintf()
    @@ Metadata
     Author: Alejandro Colomar <alx@kernel.org>
     
      ## Commit message ##
    -    libio/: Add [v]aprintf()
    +    Add [v]aprintf(3)
     
         Signed-off-by: Alejandro Colomar <alx@kernel.org>
     
    + ## libio/Makefile ##
    +@@ libio/Makefile: routines	:=							      \
    + 									      \
    + 	clearerr feof ferror fileno fputc freopen fseek getc getchar	      \
    + 	memstream pclose putc putchar rewind setbuf setlinebuf vasprintf      \
    +-	iovdprintf vscanf vsnprintf obprintf fcloseall fseeko ftello	      \
    ++	vaprintf iovdprintf vscanf vsnprintf obprintf fcloseall fseeko ftello \
    + 	freopen64 fseeko64 ftello64					      \
    + 									      \
    + 	__fbufsize __freading __fwriting __freadable __fwritable __flbf	      \
    +@@ libio/Makefile: routines_no_fortify += \
    +   iovdprintf \
    +   swprintf \
    +   vasprintf \
    ++  vaprintf \
    +   vsnprintf \
    +   vswprintf \
    +   vwprintf \
    +
      ## libio/stdio.h ##
     @@ libio/stdio.h: extern int __asprintf (char **__restrict __ptr,
      extern int asprintf (char **__restrict __ptr,
    @@ libio/vaprintf.c (new)
     +   This exception applies to code released by its copyright holders
     +   in files containing the exception.  */
     +
    -+#include "libioP.h"
    ++#include <libioP.h>
     +#include <stdarg.h>
     +#include <stddef.h>
     +#include <stdio.h>
     +
    -+char **
    ++char *
     +__vaprintf (const char *fmt, va_list args)
     +{
     +  char *p;
     +
    -+  return (__vasprintf_internal (&p, fmt, args, 0) < 0 ? NULL : p;
    ++  return __vasprintf_internal (&p, fmt, args, 0) < 0 ? NULL : p;
     +}
     +ldbl_weak_alias (__vaprintf, vaprintf)
    +
    + ## stdio-common/Makefile ##
    +@@ stdio-common/Makefile: routines := \
    +   _itoa \
    +   _itowa \
    +   asprintf \
    ++  aprintf \
    +   ctermid \
    +   cuserid \
    +   dprintf \
    +@@ stdio-common/Makefile: routines := \
    + # Exclude fortified routines from being built with _FORTIFY_SOURCE
    + routines_no_fortify += \
    +   asprintf \
    ++  aprintf \
    +   dprintf \
    +   fprintf \
    +   printf \
    +
    + ## stdio-common/aprintf.c (new) ##
    +@@
    ++/* Copyright (C) 2026 Free Software Foundation, Inc.
    ++   This file is part of the GNU C Library.
     +
    -+char **
    -+__aprintf (const char *fmt, ...)
    ++   The GNU C Library is free software; you can redistribute it and/or
    ++   modify it under the terms of the GNU Lesser General Public
    ++   License as published by the Free Software Foundation; either
    ++   version 2.1 of the License, or (at your option) any later version.
    ++
    ++   The GNU C Library is distributed in the hope that it will be useful,
    ++   but WITHOUT ANY WARRANTY; without even the implied warranty of
    ++   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    ++   Lesser General Public License for more details.
    ++
    ++   You should have received a copy of the GNU Lesser General Public
    ++   License along with the GNU C Library; if not, see
    ++   <https://www.gnu.org/licenses/>.  */
    ++
    ++#include <stdarg.h>
    ++#include <libioP.h>
    ++
    ++/* Write formatted output from FORMAT to a string which is
    ++   allocated with malloc.  */
    ++/* VARARGS1 */
    ++char *
    ++___aprintf (const char *fmt, ...)
     +{
     +  char *p;
     +  va_list ap;
     +
    -+  va_start(ap, fmt);
    -+  p = __vaprintf(fmt, ap);
    -+  va_end(ap);
    ++  va_start (ap, fmt);
    ++  if (__vasprintf_internal (&p, fmt, ap, 0) < 0)
    ++    p = NULL;
    ++  va_end (ap);
     +
     +  return p;
     +}
    -+ldbl_weak_alias (__aprintf, aprintf)
    ++ldbl_hidden_def (__aprintf, aprintf)
    ++
    ++ldbl_strong_alias (___aprintf, __aprintf)
    ++ldbl_weak_alias (___aprintf, aprintf)
-- 
2.53.0