[PATCH] regex: fix a SIZE_MAX macro redefinition warning

[Ramsay Jones <ramsay@ramsayjones.plus.com>]

Since commit 56a1a3ab ("Silence GCC's \"cast of pointer to integer of a
different size\" warning", 26-10-2015), sparse has been issuing a macro
redefinition warning for the SIZE_MAX macro. However, gcc did not issue
any such warning.

After commit 56a1a3ab, in terms of the order of #includes and #defines,
the code looked something like:

  $ cat -n junk.c
       1	#include <stddef.h>
       2
       3	#define SIZE_MAX ((size_t) -1)
       4
       5	#include <stdint.h>
       6
       7	int main(int argc, char *argv[])
       8	{
       9		return 0;
      10	}
  $
  $ gcc junk.c
  $

However, if you compile that file with -Wsystem-headers, then it will
also issue a warning. Having set -Wsystem-headers in CFLAGS, using the
config.mak file, then (on cygwin):

  $ make compat/regex/regex.o
      CC compat/regex/regex.o
  In file included from /usr/lib/gcc/x86_64-pc-cygwin/4.9.3/include/stdint.h:9:0,
                   from compat/regex/regcomp.c:21,
                   from compat/regex/regex.c:77:
  /usr/include/stdint.h:362:0: warning: "SIZE_MAX" redefined
   #define SIZE_MAX (__SIZE_MAX__)
   ^
  In file included from compat/regex/regex.c:69:0:
  compat/regex/regex_internal.h:108:0: note: this is the location of the previous definition
   # define SIZE_MAX ((size_t) -1)
   ^
  $

The compilation of the compat/regex code is somewhat unusual in that the
regex.c file directly #includes the other c files (regcomp.c, regexec.c
and regex_internal.c). Commit 56a1a3ab added an #include of <stdint.h>
to the regcomp.c file, which results in the redefinition, since this is
included after the regex_internal.h header. This header file contains a
'fallback' definition for SIZE_MAX, in order to support systems which do
not have the <stdint.h> header (the HAVE_STDINT_H macro is not defined).

In order to suppress the warning, we remove the #include of <stdint.h>
from regcomp.c and set the HAVE_STDINT_H macro, using the regex.o build
rule within the Makefile, to ensure that <stdint.h> is #included from
the regex_internal.h header.

Signed-off-by: Ramsay Jones <ramsay@ramsayjones.plus.com>
---

Hi Junio,

About seven months ago, sparse started complaining but, because gcc wasn't, I
just assumed this was a sparse bug. I put it on my sparse TODO list and pretty
much forgot about it. Tonight I decided to take a quick look and was a bit
surprised by what I found. ;-)

I spent some time worrying about the 'unconditional inclusion' of <stdint.h>
(there used to be systems that didn't supply that header that we wanted to
support), but I suspect that is now a non-issue. In any event, I don't
think this patch makes things any worse.

[Just a flavour of the rabbit holes I went down; HP-NONSTOP seems to supply
both <inttypes.h> and <stdint.h> but it doesn't supply the intptr_t and
uintptr_t types (ie it defines NO_INTPTR_T). So, I checked the C99 and C11
standards and, blow me down, but the standard states that those types are
_optional_. (C99 7.18.1.4) :-D ]

ATB,
Ramsay Jones

 Makefile               | 2 +-
 compat/regex/regcomp.c | 2 --
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index 0d59718..3f6c70a 100644
--- a/Makefile
+++ b/Makefile
@@ -1987,7 +1987,7 @@ endif
 
 ifdef NO_REGEX
 compat/regex/regex.sp compat/regex/regex.o: EXTRA_CPPFLAGS = \
-	-DGAWK -DNO_MBSUPPORT
+	-DGAWK -DNO_MBSUPPORT -DHAVE_STDINT_H
 endif
 
 ifdef USE_NED_ALLOCATOR
diff --git a/compat/regex/regcomp.c b/compat/regex/regcomp.c
index fba5986..d8bde06 100644
--- a/compat/regex/regcomp.c
+++ b/compat/regex/regcomp.c
@@ -18,8 +18,6 @@
    Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
    02110-1301 USA.  */
 
-#include <stdint.h>
-
 static reg_errcode_t re_compile_internal (regex_t *preg, const char * pattern,
 					  size_t length, reg_syntax_t syntax);
 static void re_compile_fastmap_iter (regex_t *bufp,
-- 
2.8.0