build: support thread-safety enforcement as option

Signed-off-by: Christian Brauner (Microsoft) <christian.brauner@ubuntu.com>

meson.build

@@ -148,6 +148,7 @@ want_openssl = get_option('openssl')
 want_selinux = get_option('selinux')
 want_oss_fuzz = get_option('oss-fuzz')
 want_seccomp = get_option('seccomp')
+want_thread_safety = get_option('thread-safety')
 
 srcconf.set_quoted('DEFAULT_CGROUP_PATTERN', cgrouppattern)
 if coverity
@@ -403,6 +404,8 @@ if want_oss_fuzz
     fuzzing_engine = meson.get_compiler('cpp').find_library('FuzzingEngine')
 endif
 
+srcconf.set10('ENFORCE_THREAD_SAFETY', want_thread_safety)
+
 ## PAM.
 pam = cc.find_library('pam', has_headers: 'security/pam_modules.h', required: want_pam_cgroup)
 srcconf.set10('HAVE_PAM', pam.found())
@@ -415,6 +418,28 @@ srcconf.set10('HAVE_STRCHRNUL', have)
 have = cc.has_function('openpty', prefix: '#include <pty.h>', args: '-D_GNU_SOURCE')
 srcconf.set10('HAVE_OPENPTY', have)
 
+have_func_strerror_r = cc.has_function('strerror_r', prefix: '#include <string.h>', args: '-D_GNU_SOURCE')
+srcconf.set10('HAVE_STRERROR_R', have)
+
+have_func_strerror_r_char_p = false
+
+if have_func_strerror_r
+    code = '''
+#define _GNU_SOURCE
+#include <string.h>
+int func (void) {
+    char error_string[256];
+    char *ptr = strerror_r (-2, error_string, 256);
+    char c = *strerror_r (-2, error_string, 256);
+    return c != 0 && ptr != (void*) 0L;
+}
+'''
+
+have_func_strerror_r_char_p = cc.compiles(code, name : 'strerror_r() returns char *')
+endif
+
+srcconf.set10('STRERROR_R_CHAR_P', have_func_strerror_r_char_p)
+
 ## Compiler attributes.
 foreach ccattr: [
     'fallthrough',
@@ -435,6 +460,7 @@ foreach tuple: [
     ['execveat'],
     ['faccessat'],
     ['strchrnul'],
+    ['strerror_r'],
     ['fgetln'],
     ['fsconfig'],
     ['fsmount'],

meson_options.txt

@@ -77,3 +77,6 @@ option('usernet-db-path', type: 'string', value: 'lxc/nics',
 
 option('oss-fuzz', type : 'boolean', value : 'false',
        description : 'build against oss-fuzz')
+
+option('thread-safety', type : 'boolean', value : 'true',
+       description : 'whether the build fails when thread-safe logging cannot be guaranteed')

src/lxc/log.h

@@ -304,12 +304,10 @@ __lxc_unused static inline void LXC_##LEVEL(struct lxc_log_locinfo* locinfo,	\
  * Helper macro to define errno string.
  */
 #if HAVE_STRERROR_R
-	#if !HAVE_DECL_STRERROR_R
-		#ifdef STRERROR_R_CHAR_P
-			char *strerror_r(int errnum, char *buf, size_t buflen);
-		#else
-			int strerror_r(int errnum, char *buf, size_t buflen);
-		#endif
+	#ifdef STRERROR_R_CHAR_P
+	char *strerror_r(int errnum, char *buf, size_t buflen);
+	#else
+	int strerror_r(int errnum, char *buf, size_t buflen);
 	#endif
 
 	#ifdef STRERROR_R_CHAR_P

src/tests/oss-fuzz.sh

@@ -46,6 +46,7 @@ meson setup san_build \
 	-Dseccomp=false \
 	-Db_lto=false \
 	-Db_pie=false \
+	-Dthread-safety=false \
 	-Doss-fuzz=true
 ninja -C san_build -v