win32: another attempt at a UCRT hackucrt_hack

The problem with UCRT seems to be that if a process has been
started with a non-NULL environment block passed to CreateProcess()
any subsequent call to spawnve() with a non-NULL environment pointer
fails.

Commit 5b48ca53b (win32: pass NULL to spawnve, not environ) fixed
the problem in busybox-w32 for those cases where a NULL environment
pointer was sufficient.  It didn't handle the case where the shell
passes a modified environment to its child.

All calls to spawnve() in the shell occur in a process which will
terminate whether or not the call succeeds.  It therefore doesn't
matter if we mess with the environment of this process such that
spawnve() can be passed a NULL environment pointer.  (I think.)

2 files changed, 10 insertions, 8 deletions

diff --git a/shell/ash.c b/shell/ash.c
index ad1e5ba7e..6d7066a1b 100644
--- a/shell/ash.c
+++ b/shell/ash.c
@@ -8898,9 +8898,11 @@ tryexec(IF_FEATURE_SH_STANDALONE(int applet_no,) const char *cmd, char **argv, c
 # else
                 if (APPLET_IS_NOEXEC(applet_no)) {
 # endif
+#if !defined(_UCRT)
                         clearenv();
                         while (*envp)
                                 putenv(*envp++);
+#endif
                         popredir(/*drop:*/ 1);
                         run_noexec_applet_and_exit(applet_no, cmd, argv);
                 }
@@ -8973,6 +8975,14 @@ static void shellexec(char *prog, char **argv, const char *path, int idx)
 #if !ENABLE_PLATFORM_MINGW32
         if (strchr(prog, '/') != NULL
 #else
+#if defined(_UCRT)
+        /* Avoid UCRT bug by updating parent's environment and passing a
+         * NULL environment pointer to execve(). */
+        clearenv();
+                while (*envp)
+                        putenv(*envp++);
+        envp = NULL;
+#endif
         if (has_path(prog)
 #endif
 #if ENABLE_FEATURE_SH_STANDALONE
diff --git a/win32/process.c b/win32/process.c
index 137cb6a39..812e259f4 100644
--- a/win32/process.c
+++ b/win32/process.c
@@ -268,14 +268,6 @@ spawnveq(int mode, const char *path, char *const *argv, char *const *env)
                 new_path = xasprintf("%s.", path);
         }
 
-#if defined(_UCRT)
-        if (env) {
-                char buffer[64];
-
-                sprintf(buffer, "BB_HELLO_%d", getpid());
-                SetEnvironmentVariable(buffer, "1");
-        }
-#endif
         errno = 0;
         ret = spawnve(mode, new_path ? new_path : path, new_argv, env);