[PATCH] MinGW and attribute format(printf/gnu_printf)

[Pedro Alves]

Cross building gdbserver for --host=x86_64-w64-mingw32 with gcc 4.8.4
20141219 (Fedora MinGW 4.8.4-1.fc20), I get:

  src/gdb/gdbserver/tracepoint.c: In function 'cmd_qtdp':
  src/gdb/gdbserver/tracepoint.c:2577:7: error: unknown conversion type character 'l' in format [-Werror=format=]
	 trace_debug ("Defined %stracepoint %d at 0x%s, "
	 ^
  src/gdb/gdbserver/tracepoint.c:2577:7: error: unknown conversion type character 'l' in format [-Werror=format=]
  src/gdb/gdbserver/tracepoint.c:2577:7: error: too many arguments for format [-Werror=format-extra-args]
  src/gdb/gdbserver/tracepoint.c: In function 'stop_tracing':
  src/gdb/gdbserver/tracepoint.c:3447:7: error: unknown conversion type character 'l' in format [-Werror=format=]
	 trace_debug ("Stopping the trace because "
	 ^
  src/gdb/gdbserver/tracepoint.c:3447:7: error: too many arguments for format [-Werror=format-extra-args]
  src/gdb/gdbserver/tracepoint.c: In function 'collect_data_at_tracepoint':
  src/gdb/gdbserver/tracepoint.c:4651:3: error: unknown conversion type character 'l' in format [-Werror=format=]
     trace_debug ("Making new traceframe for tracepoint %d at 0x%s, hit %" PRIu64,
     ^
  src/gdb/gdbserver/tracepoint.c:4651:3: error: too many arguments for format [-Werror=format-extra-args]
  src/gdb/gdbserver/tracepoint.c: In function 'collect_data_at_step':
  src/gdb/gdbserver/tracepoint.c:4687:3: error: unknown conversion type character 'l' in format [-Werror=format=]
     trace_debug ("Making new step traceframe for "
     ^

trace_debug is a macro that calls:

  static void trace_vdebug (const char *, ...) ATTRIBUTE_PRINTF (1, 2);

The calls that fail checking use PRIu64, etc., like:

      trace_debug ("Defined %stracepoint %d at 0x%s, "
		   "enabled %d step %" PRIu64 " pass %" PRIu64,
		   tpoint->type == fast_tracepoint ? "fast "
		   : tpoint->type == static_tracepoint ? "static " : "",
		   tpoint->number, paddress (tpoint->address), tpoint->enabled,
		   tpoint->step_count, tpoint->pass_count);

gnulib's stdio/printf module replacements may make %llu, etc. work on
mingw, instead of the MS-specific %I64u, and thus may make PRIu64
expand to %llu.  However, gcc isn't aware of that, because libiberty's
ansidecl.h defines ATTRIBUTE_PRINTF as using attribute format(printf).
But, with that format, gcc checks for MS-style format strings (%I64u).
In order to have gcc expect gnu/standard formats, we need to use
gnu_printf format instead.  Which version to use (printf/gnu_printf)
depends on msvcrt and mingw version, and so gnulib has a
configure-time check, and defines _GL_ATTRIBUTE_FORMAT_PRINTF
accordingly.

Since _GL_ATTRIBUTE_FORMAT_PRINTF is compatible with ATTRIBUTE_PRINTF,
the fix is simply to make use of the former.

gdb/ChangeLog:
2015-10-29  Pedro Alves  <palves@redhat.com>

	* common/common-defs.h (ATTRIBUTE_PRINTF): Redefine in terms of
	_GL_ATTRIBUTE_FORMAT_PRINTF after including ansidecl.h.
---
 gdb/common/common-defs.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/gdb/common/common-defs.h b/gdb/common/common-defs.h
index 2be0d7d..372b404 100644
--- a/gdb/common/common-defs.h
+++ b/gdb/common/common-defs.h
@@ -35,7 +35,16 @@
 #include <string.h>
 #include <errno.h>
 #include <alloca.h>
+
 #include "ansidecl.h"
+/* This is defined by ansidecl.h, but we prefer gnulib's version.  On
+   MinGW, gnulib might enable __USE_MINGW_ANSI_STDIO, which may or not
+   require use of attribute gnu_printf instead of printf.  gnulib
+   checks that at configure time.  Since _GL_ATTRIBUTE_FORMAT_PRINTF
+   is compatible with ATTRIBUTE_PRINTF, simply use it.  */
+#undef ATTRIBUTE_PRINTF
+#define ATTRIBUTE_PRINTF _GL_ATTRIBUTE_FORMAT_PRINTF
+
 #include "libiberty.h"
 #include "pathmax.h"
 #include "gdb/signals.h"
-- 
1.9.3