[PATCH 07/11] [C++/mingw] Define __STDC_CONSTANT_MACROS / __STDC_LIMIT_MACROS for stdint.h

Pedro Alves
2015-11-02T19:44:40Z

Cross building for --host=x86_64-w64-mingw32 using Fedora 20's g++
(gcc version 4.8.4 20141219 (Fedora MinGW 4.8.4-1.fc20)), stumbles on
many instances of:

In file included from ../../src/gdb/../include/splay-tree.h:43:0,
from ../../src/gdb/dcache.c:26:
build-gnulib/import/inttypes.h:61:3: error: #error "This file assumes that 'int' has exactly 32 bits. Please report your platform and compiler to <bug-gnulib@gnu.org>."
# error "This file assumes that 'int' has exactly 32 bits. Please report your platform and compiler to <bug-gnulib@gnu.org>."
^
make: *** [dcache.o] Error 1

That's:

#if !(INT_MIN == INT32_MIN && INT_MAX == INT32_MAX)
# error "This file assumes that 'int' has exactly 32 bits. Please report your platform and compiler to <bug-gnulib@gnu.org>."
#endif

The issue is that on some hosts that predate C++11, when using C++ one
must define __STDC_CONSTANT_MACROS/__STDC_LIMIT_MACROS to make visible
the definitions of INTMAX_C / INTMAX_MAX etc.

This was a C99 requirement that later C++11 -- the first to define
stdint.h -- removed, and then C11 removed it as well.

https://www.gnu.org/software/gnulib/manual/html_node/stdint_002eh.html
says that gnulib's stdint.h fixes this, but because we run gnulib's
configure tests with a C compiler, gnulib determines that mingw's
stdint.h is C99-compliant, and doesn't actually replace it. Actually,
even though configuring gnulib with a C++ compiler does result in
gnulib replacing stdint.h, the resulting replacement is broken for
mingw, because it defines uintptr_t incorrectly. I sent a gnulib
patch upstream to fix that, here:

https://lists.gnu.org/archive/html/bug-gnulib/2015-11/msg00004.html

but then even with that, gnulib still stumbles on other
configured-with-C++-compiler problems.

So for now, until gnulib + C++ is fixed upstream and then gdb's copy
is updated, which may take a while, I think it's best to keep
configuring gnulib in C, and define
__STDC_LIMIT_MACROS/__STDC_CONSTANT_MACROS ourselves, just like C99
intended.

gdb/ChangeLog:
2015-11-01 Pedro Alves <palves@redhat.com>

* common/common-defs.h (__STDC_CONSTANT_MACROS)
(__STDC_LIMIT_MACROS): Define before including stdint.h.
---
gdb/common/common-defs.h | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

diff --git a/gdb/common/common-defs.h b/gdb/common/common-defs.h
index 2be0d7d..59b1887 100644
--- a/gdb/common/common-defs.h
+++ b/gdb/common/common-defs.h
@@ -31,7 +31,23 @@
#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
+
+/* From:
+ https://www.gnu.org/software/gnulib/manual/html_node/stdint_002eh.html
+
+ "On some hosts that predate C++11, when using C++ one must define
+ __STDC_CONSTANT_MACROS to make visible the definitions of constant
+ macros such as INTMAX_C, and one must define __STDC_LIMIT_MACROS to
+ make visible the definitions of limit macros such as INTMAX_MAX."
+
+ gnulib doesn't fix this for us correctly yet. See:
+ https://lists.gnu.org/archive/html/bug-gnulib/2015-11/msg00004.html
+
+ Meanwhile, explicitly define these ourselves, as C99 intended. */
+#define __STDC_CONSTANT_MACROS
+#define __STDC_LIMIT_MACROS
#include <stdint.h>
+
#include <string.h>
#include <errno.h>
#include <alloca.h>
--
1.9.3