https://github.com/wxWidgets/wxWidgets/commit/da4b42688a6cd5444eefb91bf40183d88203ffca
https://bugs.gentoo.org/874441
--- a/configure
+++ b/configure
@@ -19586,6 +19586,7 @@ else
 /* end confdefs.h.  */
 
                   #include <stdio.h>
+                  #include <stdlib.h>
 
                   int main()
                   {
@@ -22300,6 +22301,7 @@ else
 
                         #include <zlib.h>
                         #include <stdio.h>
+                        #include <stdlib.h>
 
                         int main()
                         {
@@ -22422,6 +22424,7 @@ else
 
                     #include <png.h>
                     #include <stdio.h>
+                    #include <stdlib.h>
 
                     int main()
                     {
--- a/configure.in
+++ b/configure.in
@@ -1482,6 +1482,7 @@ case "${host}" in
               dnl Check the gcc version macro.
               [
                   #include <stdio.h>
+                  #include <stdlib.h>
 
                   int main()
                   {
@@ -2439,6 +2440,7 @@ if test "$wxUSE_ZLIB" != "no" ; then
                     [
                         #include <zlib.h>
                         #include <stdio.h>
+                        #include <stdlib.h>
 
                         int main()
                         {
@@ -2507,6 +2509,7 @@ if test "$wxUSE_LIBPNG" != "no" ; then
                 [
                     #include <png.h>
                     #include <stdio.h>
+                    #include <stdlib.h>
 
                     int main()
                     {
