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Re: glibc and cdefs.h

From: Bruno Haible
Subject: Re: glibc and cdefs.h
Date: Sat, 23 Jun 2018 14:44:48 +0200
User-agent: KMail/5.1.3 (Linux/4.4.0-128-generic; KDE/5.18.0; x86_64; ; )

Hi Paul,

> installed the attached patches. The first two merely merge changes from 
> glibc and cleanup, the last one fixes the bug and adds a test case.

A testdir for 'random_r' produces a compilation failure on FreeBSD 11:

-I/home/bruno/include -Wall  -g -O2 -MT random_r.o -MD -MP -MF 
.deps/random_r.Tpo -c -o random_r.o ../../gllib/random_r.c
In file included from ../../gllib/random_r.c:68:
In file included from ./stdlib.h:36:
/usr/include/stdlib.h:175:56: error: expected ')'
int      posix_memalign(void **, size_t, size_t) __nonnull(1); /* (ADV) */
1 error generated.

The reason are these definitions:

#define __nonnull(params) __attribute__ ((__nonnull__ params))

#define __nonnull(x) __attribute__((__nonnull__(x)))

int      posix_memalign(void **, size_t, size_t) __nonnull(1); /* (ADV) */

The patch below fixes it, by avoiding to define __nonnull.

But the problem is deeper than that: <libc-config.h> undefines more than
60 symbols that are prefixed with __ and replaces them with glibc's definition.
But then, compilation units such as lib/malloc/scratch_buffer_grow.c go on to
include header files such as <stdbool.h>, <stddef.h>, <stdlib.h>, which
references the gnulib replacements, which end up including the system headers
<stdbool.h>, <stddef.h>, <stdlib.h> - but with the glibc definitions of
the 60 symbols in effect.

IMO the only way to reliably use <libc-config.h> would be that after
including it, you don't include any system headers any more.

2018-06-23  Bruno Haible  <address@hidden>

        libc-config: Fix conflict with FreeBSD include files.
        * lib/cdefs.h (__nonnull): Remove definition.
        * lib/libc-config.h (__nonnull): Remove undefinition.

diff --git a/lib/cdefs.h b/lib/cdefs.h
index f6c20fe..76325c5 100644
--- a/lib/cdefs.h
+++ b/lib/cdefs.h
@@ -282,13 +282,10 @@
 # define __attribute_format_strfmon__(a,b) /* Ignore */
-/* The nonull function attribute allows to mark pointer parameters which
-   must not be NULL.  */
-#if __GNUC_PREREQ (3,3)
-# define __nonnull(params) __attribute__ ((__nonnull__ params))
-# define __nonnull(params)
+/* The nonnull function attribute allows to mark pointer parameters which
+   must not be NULL.
+   In Gnulib we use the macro _GL_ARG_NONNULL instead of __nonnull, because
+   __nonnull is defined in an incompatible way in FreeBSD's include files.  */
 /* If fortification mode, we warn about unused results of certain
    function calls which can lead to problems.  */
diff --git a/lib/libc-config.h b/lib/libc-config.h
index 747d620..14f0bb4 100644
--- a/lib/libc-config.h
+++ b/lib/libc-config.h
@@ -136,7 +136,6 @@
 #undef __glibc_macro_warning1
 #undef __glibc_unlikely
 #undef __inline
-#undef __nonnull
 #undef __ptr_t
 #undef __restrict
 #undef __restrict_arr

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