PR#6903: Unix.execvpe doesn't change environment on Cygwin

Old implementation was based on changing the "environ" variable and calling "execvp".  It doesn't work under Cygwin and possibly other OS.

New implementation builds on "execve" after searching the executable in PATH ourselves.

Changes

@@ -277,6 +277,9 @@ Next version (4.05.0):
   uninitialized caml_global_data (only changes the bytecode behavior)
   (Gabriel Scherer, review by Xavier Leroy)
 
+- PR#6903: Unix.execvpe doesn't change environment on Cygwin
+  (Xavier Leroy)
+
 - PR#7216, GPR#949: don't require double parens in Functor((val x))
   (Jacques Garrigue, review by Valentin Gatien-Baron)
 

otherlibs/unix/execvp.c

@@ -15,6 +15,8 @@
 
 #include <caml/mlvalues.h>
 #include <caml/memory.h>
+#define CAML_INTERNALS
+#include <caml/osdeps.h>
 #include "unixsupport.h"
 
 #ifndef _WIN32
@@ -30,22 +32,23 @@ CAMLprim value unix_execvp(value path, value args)
   caml_stat_free((char *) argv);
   uerror("execvp", path);
   return Val_unit;                  /* never reached, but suppress warnings */
-                                /* from smart compilers */
+                                    /* from smart compilers */
 }
 
 CAMLprim value unix_execvpe(value path, value args, value env)
 {
+  char * exefile;
   char ** argv;
-  char ** saved_environ;
+  char ** envp;
   caml_unix_check_path(path, "execvpe");
+  exefile = caml_search_exe_in_path(String_val(path));
   argv = cstringvect(args, "execvpe");
-  saved_environ = environ;
-  environ = cstringvect(env, "execvpe");
-  (void) execvp(String_val(path), argv);
+  envp = cstringvect(env, "execvpe");
+  (void) execve(exefile, argv, envp);
+  caml_stat_free(exefile);
   caml_stat_free((char *) argv);
-  caml_stat_free((char *) environ);
-  environ = saved_environ;
-  uerror("execvp", path);
+  caml_stat_free((char *) envp);
+  uerror("execvpe", path);
   return Val_unit;                  /* never reached, but suppress warnings */
-                                /* from smart compilers */
+                                    /* from smart compilers */
 }