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[PATCH] stdio: fix use of PRIdMAX on modern mingw

From: Eric Blake
Subject: [PATCH] stdio: fix use of PRIdMAX on modern mingw
Date: Mon, 5 Jan 2015 16:03:18 -0700

Commit cf88e56ab broke the use of PRIdMAX and friends on modern
mingw64 installations.  Basically, when requesting
_USE_MINGW_ANSI_STDIO, not only does mingw turn on support for %lld,
it also rewrites <inttypes.h> to provide PRIdMAX as "lld" instead of
"I64d" (but only when <stdio.h> is also included).  But if a user is
NOT using the gnulib printf module, gnulib's <stdio.h> was still
giving printf() the system printf attribute, which causes the
compiler to then complain about an unknown %lld specifier, even though
we know we don't need to use the non-standard %I64d.  So this patch
adds a configure-time probe that should work with older gcc (which
does not differentiate between printf flavors) and older mingw (where
_USE_MINGW_ANSI_STDIO has no impact on behavior), while fixing the
mismatch in flavors on modern systems.

* m4/stdio_h.m4 (gl_STDIO_H): Probe for printf flavor via inttypes.
* lib/stdio.in.h (_GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM): Use result
to work with modern mingw.

Signed-off-by: Eric Blake <address@hidden>

Took me a while to figure out how to solve this problem even when
cross-compiling, until I realized that the preprocessor + grep is
sufficient to sniff out the final definition of a macro.

 ChangeLog      |  7 +++++++
 lib/stdio.in.h |  7 ++++++-
 m4/stdio_h.m4  | 20 +++++++++++++++++++-
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 9f5611d..6f49589 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2015-01-05  Eric Blake  <address@hidden>
+       stdio: fix use of PRIdMAX on modern mingw
+       * m4/stdio_h.m4 (gl_STDIO_H): Probe for printf flavor via inttypes.
+       * lib/stdio.in.h (_GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM): Use result
+       to work with modern mingw.
 2015-01-04  Paul Eggert  <address@hidden>

        lib-symbol-versions: cache script check
diff --git a/lib/stdio.in.h b/lib/stdio.in.h
index fb2fb70..9b545b8 100644
--- a/lib/stdio.in.h
+++ b/lib/stdio.in.h
@@ -84,8 +84,13 @@
    except that it indicates to GCC that the supported format string directives
    are the ones of the system printf(), rather than the ones standardized by
    ISO C99 and POSIX.  */
-#define _GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM(formatstring_parameter, 
first_argument) \
+# define _GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM(formatstring_parameter, 
first_argument) \
+  _GL_ATTRIBUTE_FORMAT_PRINTF (formatstring_parameter, first_argument)
+# define _GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM(formatstring_parameter, 
first_argument) \
   _GL_ATTRIBUTE_FORMAT ((__printf__, formatstring_parameter, first_argument))

    indicates to GCC that the function takes a format string and arguments,
diff --git a/m4/stdio_h.m4 b/m4/stdio_h.m4
index 4217338..e0c4bde 100644
--- a/m4/stdio_h.m4
+++ b/m4/stdio_h.m4
@@ -1,4 +1,4 @@
-# stdio_h.m4 serial 43
+# stdio_h.m4 serial 44
 dnl Copyright (C) 2007-2015 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -12,6 +12,24 @@ AC_DEFUN([gl_STDIO_H],

+  dnl Determine whether __USE_MINGW_ANSI_STDIO makes printf and
+  dnl inttypes.h behave like gnu instead of system; we must give our
+  dnl printf wrapper the right attribute to match.
+  AC_CACHE_CHECK([whether inttypes macros match system or gnu printf],
+    [gl_cv_func_printf_attribute_flavor],
+    [AC_EGREP_CPP([findme .(ll|j)d. findme],
+      [#define __STDC_FORMAT_MACROS 1
+       #include <stdio.h>
+       #include <inttypes.h>
+       findme PRIdMAX findme
+      ], [gl_cv_func_printf_attribute_flavor=gnu],
+      [gl_cv_func_printf_attribute_flavor=system])])
+  if test "$gl_cv_func_printf_attribute_flavor" = gnu; then
+      [Define to 1 if printf and friends should be labeled with
+       attribute "__gnu_printf__" instead of "__printf__"])
+  fi
   dnl No need to create extra modules for these functions. Everyone who uses
   dnl <stdio.h> likely needs them.

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