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Re: [PATCH 07/11] [C++/mingw] Define __STDC_CONSTANT_MACROS / __STDC_LIMIT_MACROS for stdint.h
- From: Pedro Alves <palves at redhat dot com>
- To: Simon Marchi <simon dot marchi at ericsson dot com>, gdb-patches at sourceware dot org
- Date: Tue, 03 Nov 2015 15:13:06 +0000
- Subject: Re: [PATCH 07/11] [C++/mingw] Define __STDC_CONSTANT_MACROS / __STDC_LIMIT_MACROS for stdint.h
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- References: <1446492970-21432-1-git-send-email-palves at redhat dot com> <1446492970-21432-8-git-send-email-palves at redhat dot com> <5637CBC9 dot 2050404 at ericsson dot com> <5638BD73 dot 8000706 at ericsson dot com> <5638BF81 dot 5070705 at redhat dot com> <5638C168 dot 1020603 at ericsson dot com>
On 11/03/2015 02:15 PM, Simon Marchi wrote:
> On 15-11-03 09:06 AM, Pedro Alves wrote:
>> Isn't this a case of "don't do that (CFLAGS), then" ?
>
> Maybe. I was thinking somebody might have this defined in their
> development environment, but I agree it's unlikely.
>
As discussed on irc, -DFOO actually gives the symbol value 1, so
Simon got the error because I had defined the symbols with no value, like:
#define __STDC_CONSTANT_MACROS
So if we define the symbols with value 1, then the error is gone.
Here's the updated patch.
-------
>From a710518eff022b6ab452415ab1191dc5c748dfe5 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Sun, 1 Nov 2015 17:33:36 +0000
Subject: [PATCH] [C++/mingw] Define __STDC_CONSTANT_MACROS /
__STDC_LIMIT_MACROS for stdint.h
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..548fe42 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 1
+#define __STDC_LIMIT_MACROS 1
#include <stdint.h>
+
#include <string.h>
#include <errno.h>
#include <alloca.h>
--
1.9.3