win32: revert changes related to environment variables

Revert the change to mingw_putenv() in the previous commit.

When compiling for MSVCRT (i.e. not for UCRT) revert some of the
changes from commit 5b48ca53b (win32: pass NULL to spawnve, not
environ).

(GitHub issue #250)

1 files changed, 12 insertions, 8 deletions

diff --git a/win32/env.c b/win32/env.c
index 5de581e3d..4d4e9c8fd 100644
--- a/win32/env.c
+++ b/win32/env.c
@@ -78,7 +78,7 @@ int clearenv(void)
 
 int mingw_putenv(const char *env)
 {
-        char *s;
+        char *s, **envp;
         int ret = 0;
 
         if ( (s=strchr(env, '=')) == NULL ) {
@@ -90,13 +90,17 @@ int mingw_putenv(const char *env)
                 return _putenv(env);
         }
         else {
-                /* set empty value using WIN32 API*/
-                char *name = xstrdup(env);
-                name[s - env] = '\0';
-                SetEnvironmentVariable(name, "");
-                free(name);
-                /* set a dummy variable to force CRT housekeeping */
-                _putenv("BB_DUMMY=0");
+                /* set empty value by setting a non-empty one then truncating */
+                char *envstr = xasprintf("%s0", env);
+                ret = _putenv(envstr);
+
+                for (envp = environ; *envp; ++envp) {
+                        if (strcmp(*envp, envstr) == 0) {
+                                (*envp)[s - env + 1] = '\0';
+                                break;
+                        }
+                }
+                free(envstr);
         }
 
         return ret;