On 10/16/2016 11:17 AM, Bruno Haible wrote: > There are two problems: > > 1) argp-help.c uses STRERROR_R_CHAR_P, which is defined by the macro > AC_FUNC_STRERROR_R, but argp.m4 does not require it (only error.m4 does). > > 2) When the strerror_r-posix module is in place, the results of > AC_FUNC_STRERROR_R have to be ignored, because they don't reflect the > situation after > #define strerror_r rpl_strerror_r > > With the following proposed patches, we arrive at a sane situation without > warning, and > > $ gcc ... -E argp-help.c | grep strerror_r > extern char *strerror_r (int __errnum, char *__buf, size_t __buflen) > extern int rpl_strerror_r (int errnum, char *buf, size_t buflen) > __attribute__ ((__nonnull__ (2))) > if (rpl_strerror_r (errnum, buf, sizeof buf) == 0) > >
>
> 2016-10-16 Bruno Haible <br...@clisp.org>
>
> Fix conflict between strerror_r-posix module and AC_FUNC_STRERROR_R.
> * m4/strerror_r.m4 (gl_FUNC_STRERROR_R): Override the values set by the
> AC_FUNC_STRERROR_R macro. Define HAVE_DECL_STRERROR_R_ORIG.
> * lib/strerror_r.c: Use HAVE_DECL_STRERROR_R_ORIG instead of
> HAVE_DECL_STRERROR_R.
This commit causes weird compilation failures; in particular, trying to
use it on libvirt causes -Wformat to no longer be used. Why? Because it
interferes with all future configure probes:
> +
> + # Overwrite the findings of AC_FUNC_STRERROR_R (for code that uses that).
> + AC_REQUIRE([AC_FUNC_STRERROR_R])
> + AC_DEFINE([HAVE_DECL_STRERROR_R], [1])
> + AC_DEFINE([STRERROR_R_CHAR_P], [0])
Symptoms of the failure, as seen in config.log, are as follows:
configure:17696: checking for strerror_r
configure:17696: result: yes
configure:17705: checking whether strerror_r returns char *
configure:17729: gcc -c -g conftest.c >&5
configure:17729: $? = 0
configure:17767: result: yes
configure:17818: checking for external symbol _system_configuration
configure:17836: gcc -o conftest -g conftest.c >&5
conftest.c:216:0: warning: "STRERROR_R_CHAR_P" redefined
#define STRERROR_R_CHAR_P 0
conftest.c:213:0: note: this is the location of the previous definition
#define STRERROR_R_CHAR_P 1
conftest.c:218:27: fatal error: sys/systemcfg.h: No such file or directory
#include <sys/systemcfg.h>
^
which then results in probes for -Werror failing where they used to
succeed, and in libvirt's case this causes a probe for '-Wformat
-Werror' to be incorrectly diagnosed.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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