On many systems (esp. BSD ones), building a recent m4 snapshot produces these
warnings:
--------------------------------------------------------------------------------
CC regex.o
In file included from ../../lib/regex_internal.h:57:0,
from ../../lib/regex.c:70:
../../lib/regcomp.c: In function 'rpl_regfree':
../../lib/glthread/lock.h:640:38: warning: statement with no effect
[-Wunused-value]
# define glthread_lock_destroy(NAME) 0
^
../../lib/regex_internal.h:60:26: note: in expansion of macro
'glthread_lock_destroy'
# define lock_fini(lock) glthread_lock_destroy (&(lock))
^
../../lib/regcomp.c:638:7: note: in expansion of macro 'lock_fini'
lock_fini (dfa->lock);
^
../../lib/regcomp.c: In function 're_compile_internal':
../../lib/glthread/lock.h:640:38: warning: statement with no effect
[-Wunused-value]
# define glthread_lock_destroy(NAME) 0
^
../../lib/regex_internal.h:60:26: note: in expansion of macro
'glthread_lock_destroy'
# define lock_fini(lock) glthread_lock_destroy (&(lock))
^
../../lib/regcomp.c:781:7: note: in expansion of macro 'lock_fini'
lock_fini (dfa->lock);
^
../../lib/glthread/lock.h:640:38: warning: statement with no effect
[-Wunused-value]
# define glthread_lock_destroy(NAME) 0
^
../../lib/regex_internal.h:60:26: note: in expansion of macro
'glthread_lock_destroy'
# define lock_fini(lock) glthread_lock_destroy (&(lock))
^
../../lib/regcomp.c:814:7: note: in expansion of macro 'lock_fini'
lock_fini (dfa->lock);
^
../../lib/regexec.c: In function 'rpl_regexec':
../../lib/glthread/lock.h:638:35: warning: statement with no effect
[-Wunused-value]
# define glthread_lock_lock(NAME) 0
^
../../lib/regex_internal.h:61:26: note: in expansion of macro
'glthread_lock_lock'
# define lock_lock(lock) glthread_lock_lock (&(lock))
^
../../lib/regexec.c:214:3: note: in expansion of macro 'lock_lock'
lock_lock (dfa->lock);
^
../../lib/glthread/lock.h:639:37: warning: statement with no effect
[-Wunused-value]
# define glthread_lock_unlock(NAME) 0
^
../../lib/regex_internal.h:62:28: note: in expansion of macro
'glthread_lock_unlock'
# define lock_unlock(lock) glthread_lock_unlock (&(lock))
^
../../lib/regexec.c:221:3: note: in expansion of macro 'lock_unlock'
lock_unlock (dfa->lock);
^
In file included from ../../lib/regex.c:74:0:
../../lib/regexec.c:198:13: warning: unused variable 'dfa' [-Wunused-variable]
re_dfa_t *dfa = preg->buffer;
^
In file included from ../../lib/regex_internal.h:57:0,
from ../../lib/regex.c:70:
../../lib/regexec.c: In function 're_search_stub':
../../lib/glthread/lock.h:638:35: warning: statement with no effect
[-Wunused-value]
# define glthread_lock_lock(NAME) 0
^
../../lib/regex_internal.h:61:26: note: in expansion of macro
'glthread_lock_lock'
# define lock_lock(lock) glthread_lock_lock (&(lock))
^
../../lib/regexec.c:391:3: note: in expansion of macro 'lock_lock'
lock_lock (dfa->lock);
^
../../lib/glthread/lock.h:639:37: warning: statement with no effect
[-Wunused-value]
# define glthread_lock_unlock(NAME) 0
^
../../lib/regex_internal.h:62:28: note: in expansion of macro
'glthread_lock_unlock'
# define lock_unlock(lock) glthread_lock_unlock (&(lock))
^
../../lib/regexec.c:455:3: note: in expansion of macro 'lock_unlock'
lock_unlock (dfa->lock);
^
In file included from ../../lib/regex.c:74:0:
../../lib/regexec.c:378:13: warning: unused variable 'dfa' [-Wunused-variable]
re_dfa_t *dfa = bufp->buffer;
^
--------------------------------------------------------------------------------
These warnings are indicating that the regex module is being built for multi-
threading, while at the same time the Gnulib 'lock' module is being optimized
for single-threading (due to the gl_DISABLE_THREADS invocation in configure.ac).
According to the Gnulib documentation section "Optimizations of multithreaded
code" several more optimizations can be enabled. This patch
- enables these single-threading optimizations,
- by doing so, gets rid of the warnings in regex.c,
- causes no test failures.
OK to push?
>From 611fa6cd92671318b22e70f931db695a58ecdaf3 Mon Sep 17 00:00:00 2001
From: Bruno Haible <br...@clisp.org>
Date: Thu, 13 May 2021 10:49:13 +0200
Subject: [PATCH] Enable more single-thread optimizations in gnulib code.
* configure.ac (GNULIB_REGEX_SINGLE_THREAD, GNULIB_MBRTOWC_SINGLE_THREAD,
GNULIB_WCHAR_SINGLE_LOCALE): Define as C macros.
---
configure.ac | 3 +++
1 file changed, 3 insertions(+)
diff --git a/configure.ac b/configure.ac
index 04a7d4b..517666f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -42,6 +42,9 @@ gl_ASSERT_NO_GNULIB_POSIXCHECK
# M4 is single-threaded; so we can optimize gnulib code by using this:
gl_DISABLE_THREADS
+AC_DEFINE([GNULIB_REGEX_SINGLE_THREAD], [1], [Define to optimize regex.])
+AC_DEFINE([GNULIB_MBRTOWC_SINGLE_THREAD], [1], [Define to optimize mbrtowc.])
+AC_DEFINE([GNULIB_WCHAR_SINGLE_LOCALE], [1], [Define to optimize mbrtowc.])
AC_ARG_ENABLE([gcc-warnings],
[AS_HELP_STRING([--enable-gcc-warnings],
--
2.7.4
