[mkstemps] Check for mkstemps function

musl has it, but it was not detected

config2.h.in

@@ -822,6 +822,9 @@
 /* Define to 1 if you have the `__argz_stringify' function. */
 #mesondefine HAVE___ARGZ_STRINGIFY
 
+/* Define to 1 if you have the `mkstemps' function. */
+#mesondefine HAVE_MKSTEMPS
+
 /* Define as const if the declaration of iconv() needs const. */
 #mesondefine ICONV_CONST
 
@@ -916,6 +919,11 @@
 #ifndef _GNU_SOURCE
 # define _GNU_SOURCE
 #endif
+/* Enable DEFAULT_SOURCE */
+#ifndef _DEFAULT_SOURCE
+# define _DEFAULT_SOURCE
+#endif
+
 /* Enable threading extensions on Solaris.  */
 #ifndef _POSIX_PTHREAD_SEMANTICS
 # undef _POSIX_PTHREAD_SEMANTICS

configure.ac

@@ -324,6 +324,7 @@ AC_CHECK_FUNCS(geteuid, HAVE_GETEUID=yes)
 AC_CHECK_FUNCS(wcwidth, HAVE_WCWIDTH=yes)
 
 AC_CHECK_FUNCS(fork)
+AC_CHECK_FUNCS(mkstemps)
 
 # These aren't probably needed now, as they are commented in links.h.
 # I've no idea about their historical background, but I keep them here

meson.build

@@ -689,6 +689,10 @@ if compiler.has_function('gnutls_certificate_set_x509_system_trust', prefix: '#i
     conf_data.set('HAVE_GNUTLS_CERTIFICATE_SET_X509_SYSTEM_TRUST', 1)
 endif
 
+if compiler.has_function('mkstemps', prefix: '#include <stdlib.h>', args: '-D_GNU_SOURCE')
+    conf_data.set('HAVE_MKSTEMPS', 1)
+endif
+
 conf_data.set('ICONV_CONST', true)
 
 sysconfdir = get_option('prefix') / get_option('sysconfdir')/'elinks'

src/osdep/osdep.c

@@ -1019,7 +1019,7 @@ get_system_str(int xwin)
 	return xwin ? SYSTEM_STR "-xwin" : SYSTEM_STR;
 }
 
-#if _DEFAULT_SOURCE || _SVID_SOURCE || _BSD_SOURCE
+#ifdef HAVE_MKSTEMPS
 
 /* tempnam() replacement without races */