Add C11 threads.h implementation in addition to pthread implementation for multithreaded encoding.

configure.ac

@@ -53,7 +53,7 @@ AM_PROG_CC_C_O
 AC_C_INLINE
 AC_C_TYPEOF
 
-AC_CHECK_HEADERS([stdint.h stdbool.h inttypes.h byteswap.h sys/auxv.h sys/param.h sys/ioctl.h sys/time.h termios.h x86intrin.h cpuid.h arm_neon.h])
+AC_CHECK_HEADERS([stdint.h stdbool.h inttypes.h byteswap.h sys/auxv.h sys/param.h sys/ioctl.h sys/time.h termios.h x86intrin.h cpuid.h arm_neon.h threads.h])
 
 if test "x$ac_cv_header_stdint_h" != xyes -o "x$ac_cv_header_stdbool_h" != xyes; then
 AC_MSG_ERROR("Header stdint.h and/or stdbool.h not found")
@@ -379,15 +379,21 @@ HAVE_PTHREAD=no
 if test "x$enable_multithreading" != "xno" ; then
 	AX_PTHREAD([
 		HAVE_PTHREAD=yes
-		AC_DEFINE(HAVE_PTHREAD,1,[Define if pthread is enabled])
+		AC_DEFINE([HAVE_PTHREAD],1,[Define if multithreading is enable and pthread is available])
 		LIBS="$PTHREAD_LIBS $LIBS"
 		CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
 		CXXFLAGS="$CXXFLAGS $PTHREAD_CFLAGS"
 		CC="$PTHREAD_CC"
 		CXX="$PTHREAD_CXX"
 		],[HAVE_PTHREAD=no])
-	if test "x${HAVE_PTHREAD}" = "xno"; then
-		AC_MSG_WARN("pthread support, needed for multithreading, is not found")
+	if test  "x${HAVE_PTHREAD}" = "xno" -a "x$ac_cv_header_threads_h" = "xyes"; then
+		HAVE_C11THREADS=yes
+		AC_DEFINE([HAVE_C11THREADS],1,[Define if multithreading is enable and <threads.h> is available])
+	else
+		HAVE_C11THREADS=no
+	fi
+	if test "x${HAVE_PTHREAD}" = "xno" -a "x${HAVE_C11THREADS}" = "xno"; then
+		AC_MSG_WARN("pthread or C11 threads support, needed for multithreading, are not found")
 	fi
 fi
 
@@ -616,7 +622,13 @@ fi
 	echo "    Compiler is Clang : ....................... ${xiph_cv_c_compiler_clang}"
 	echo "    Asm optimizations : ....................... ${asm_optimisation}"
 	echo "    Ogg/FLAC support : ........................ ${have_ogg}"
-	echo "    Multithreading   : ........................ ${HAVE_PTHREAD}"
+if test "x${HAVE_C11THREADS}" = "xyes" ; then
+	echo "    Multithreading   : ........................ C11 threads"
+elif test "x${HAVE_PTHREAD}" = "xyes" ; then
+	echo "    Multithreading   : ........................ pthread"
+else
+	echo "    Multithreading   : ........................ no"
+fi
 	echo "    Stack protector  : ........................ ${enable_stack_smash_protection}"
 	echo "    Fuzzing support (Clang only) : ............ ${have_oss_fuzzers}"
 echo

include/share/Makefile.am

@@ -5,6 +5,7 @@ SUBDIRS = grabbag
 EXTRA_DIST = \
 	alloc.h \
 	compat.h \
+	compat_threads.h \
 	endswap.h \
 	getopt.h \
 	grabbag.h \

include/share/compat_threads.h

@@ -0,0 +1,124 @@
+/* libFLAC - Free Lossless Audio Codec library
+ * Copyright (C) 2025 Jörn Heusipp
+ * Copyright (C) 2025 Xiph.Org Foundation
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * - Neither the name of the Xiph.org Foundation nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef FLAC__SHARE__COMPAT_THREADS_H
+#define FLAC__SHARE__COMPAT_THREADS_H
+
+#if defined(HAVE_C11THREADS) || defined(HAVE_PTHREAD)
+#define FLAC__USE_THREADS
+#endif
+
+#ifdef FLAC__USE_THREADS
+#if defined(HAVE_C11THREADS)
+#include <threads.h>
+#elif defined(HAVE_PTHREAD)
+#include <errno.h>
+#include <stddef.h>
+#include <pthread.h>
+#endif
+#endif
+
+
+#ifdef FLAC__USE_THREADS
+
+#if defined(HAVE_C11THREADS)
+
+#define FLAC__thrd_success                   thrd_success
+#define FLAC__thrd_busy                      thrd_busy
+#define FLAC__thrd_nomem                     thrd_nomem
+
+#define FLAC__thrd_t                         thrd_t
+#define FLAC__thrd_create(thread, func, arg) thrd_create(thread, func, arg)
+#define FLAC__thrd_join(thread, result)      thrd_join(thread, result)
+
+#define FLAC__mtx_plain                      mtx_plain
+#define FLAC__mtx_t                          mtx_t
+#define FLAC__mtx_init(mutex, type)          mtx_init(mutex, type)
+#define FLAC__mtx_trylock(mutex)             mtx_trylock(mutex)
+#define FLAC__mtx_lock(mutex)                mtx_lock(mutex)
+#define FLAC__mtx_unlock(mutex)              mtx_unlock(mutex)
+#define FLAC__mtx_destroy(mutex)             mtx_destroy(mutex)
+
+#define FLAC__cnd_t                          cnd_t
+#define FLAC__cnd_init(cv)                   cnd_init(cv)
+#define FLAC__cnd_broadcast(cv)              cnd_broadcast(cv)
+#define FLAC__cnd_signal(cv)                 cnd_signal(cv)
+#define FLAC__cnd_wait(cv, mutex)            cnd_wait(cv, mutex)
+#define FLAC__cnd_destroy(cv)                cnd_destroy(cv)
+
+#define FLAC__thread_return_type             int
+#define FLAC__thread_default_return_value    0
+
+#elif defined(HAVE_PTHREAD)
+
+/* This is not meant to be a full implementation of C11 threads on top of
+ * pthreads.
+ * Just enough is implemented to provide the interfaces that libFLAC uses
+ * currently.
+ * A full implementation would certainly be possible, but there already are
+ * various other open source projects dedicated to providing pthread <-> C11
+ * threads wrappers both ways. FLAC wants to avoid the additional dependency
+ * here, and provides this reduced wrapper itself.
+ */
+
+#define FLAC__thrd_success                   0
+#define FLAC__thrd_busy                      EBUSY
+#define FLAC__thrd_nomem                     ENOMEM
+
+#define FLAC__thrd_t                         pthread_t
+#define FLAC__thrd_create(thread, func, arg) pthread_create(thread, NULL, func, arg)
+#define FLAC__thrd_join(thread, result)      pthread_join(thread, result)
+
+#define FLAC__mtx_plain                      NULL
+#define FLAC__mtx_t                          pthread_mutex_t
+#define FLAC__mtx_init(mutex, type)          ((pthread_mutex_init(mutex, type) == 0) ? FLAC__thrd_success : FLAC__thrd_nomem)
+#define FLAC__mtx_trylock(mutex)             ((pthread_mutex_trylock(mutex) == 0) ? FLAC__thrd_success : FLAC__thrd_busy)
+#define FLAC__mtx_lock(mutex)                pthread_mutex_lock(mutex)
+#define FLAC__mtx_unlock(mutex)              pthread_mutex_unlock(mutex)
+#define FLAC__mtx_destroy(mutex)             pthread_mutex_destroy(mutex)
+
+#define FLAC__cnd_t                          pthread_cond_t
+#define FLAC__cnd_init(cv)                   ((pthread_cond_init(cv, NULL) == 0) ? FLAC__thrd_success : FLAC__thrd_nomem)
+#define FLAC__cnd_broadcast(cv)              pthread_cond_broadcast(cv)
+#define FLAC__cnd_signal(cv)                 pthread_cond_signal(cv)
+#define FLAC__cnd_wait(cv, mutex)            pthread_cond_wait(cv, mutex)
+#define FLAC__cnd_destroy(cv)                pthread_cond_destroy(cv)
+
+#define FLAC__thread_return_type             void *
+#define FLAC__thread_default_return_value    NULL
+
+#endif
+
+#endif
+
+
+#endif /* FLAC__SHARE__COMPAT_THREADS_H */