classpath, csharpexec: Avoid "candidate for attribute 'malloc'" warning

[Bruno Haible]

In GNU gettext, I see these warnings when compiling with gcc 13, warnings,
and -O2:

gettext-tools/gnulib-lib/classpath.c:97:1: warning: function might be candidate 
for attribute 'malloc' [-Wsuggest-attribute=malloc]
gettext-tools/gnulib-lib/csharpexec.c:36:23: warning: function might be 
candidate for attribute 'malloc' [-Wsuggest-attribute=malloc]
gettext-tools/gnulib-lib/csharpexec.c:57:23: warning: function might be 
candidate for attribute 'malloc' [-Wsuggest-attribute=malloc]

This patch follows the advice.


2023-06-03  Bruno Haible  <bruno@clisp.org>

        classpath, csharpexec: Avoid "candidate for attribute 'malloc'" warning.
        * lib/classpath.h (set_classpath): Mark with attribute 'malloc'.

diff --git a/lib/classpath.h b/lib/classpath.h
index abcb4cbe40..65123140cf 100644
--- a/lib/classpath.h
+++ b/lib/classpath.h
@@ -15,6 +15,11 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
 
+/* This file uses _GL_ATTRIBUTE_MALLOC.  */
+#if !_GL_CONFIG_H_INCLUDED
+ #error "Please include config.h first."
+#endif
+
 /* Return the new CLASSPATH value.  The given classpaths are prepended to
    the current CLASSPATH value.   If use_minimal_classpath, the current
    CLASSPATH is ignored.  */
@@ -25,7 +30,8 @@ extern char * new_classpath (const char * const *classpaths,
 /* Set CLASSPATH and returns a safe copy of its old value.  */
 extern char * set_classpath (const char * const *classpaths,
                              unsigned int classpaths_count,
-                             bool use_minimal_classpath, bool verbose);
+                             bool use_minimal_classpath, bool verbose)
+     _GL_ATTRIBUTE_MALLOC;
 
 /* Restore CLASSPATH to its previous value.  */
 extern void reset_classpath (char *old_classpath);