bug#24956: 26.0.50; On Windows, setting PATH in compilation-environment has no effect

[Noam Postavsky <npostavs@users.sourceforge.net>]

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On Tue, Nov 22, 2016 at 11:01 AM, Eli Zaretskii <eliz@gnu.org> wrote:
>
> Why not compare in using _strnicmp instead of Fcompare_strings?  That
> would save you the need to cons Lisp strings, and will be more
> efficient (Fcompare_strings is quite complex).  Not that speed matters
> in this case, but it's just looks strange to me.  Am I missing
> something?

Oops. Looking at Fupcase, I had somehow thought that unibyte vs
multibyte would be a problem (and hence I should use Fcompare_strings
to hide the details), but actually (as I think you've mentioned
before) that's not the case for environment variables.

Here's a new patch.

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From ecb8a7ea028235e67a955e63c5ee1ca5d574b04f Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Fri, 18 Nov 2016 16:26:53 -0500
Subject: [PATCH v3] Upcase Path and ComSpec in process-environment

Since 2016-07-18 "Keep w32 environment settings internal only", the
upcasing of environment variables "Path" and "ComSpec" occured after
initializing process-environment.  This meant that Lisp code trying to
override "PATH" environment had no effect (Bug #24956).

* src/w32.c (init_environment): Upcase the "Path" and "ComSpec" entries
in Vprocess_environment.
---
 src/w32.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/src/w32.c b/src/w32.c
index ad7d94a..086c1ac 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -2863,12 +2863,29 @@ init_environment (char ** argv)
      The same applies to COMSPEC.  */
   {
     char ** envp;
+    const char *path = "PATH=";
+    int path_len = strlen (path);
+    const char *comspec = "COMSPEC=";
+    int comspec_len = strlen (comspec);
 
     for (envp = environ; *envp; envp++)
-      if (_strnicmp (*envp, "PATH=", 5) == 0)
-	memcpy (*envp, "PATH=", 5);
-      else if (_strnicmp (*envp, "COMSPEC=", 8) == 0)
-	memcpy (*envp, "COMSPEC=", 8);
+      if (_strnicmp (*envp, path, path_len) == 0)
+        memcpy (*envp, path, path_len);
+      else if (_strnicmp (*envp, comspec, comspec_len) == 0)
+        memcpy (*envp, comspec, comspec_len);
+
+    /* Make the same modification to `process-environment' which has
+       already been initialized in set_initial_environment.  */
+    for (Lisp_Object env = Vprocess_environment; CONSP (env); env = XCDR (env))
+    {
+      Lisp_Object entry = XCAR (env);
+      if (_strnicmp (SDATA (entry), path, path_len) == 0)
+        for (int i = 0; i < path_len; i++)
+          SSET (entry, i, path[i]);
+      else if (_strnicmp (SDATA (entry), comspec, comspec_len) == 0)
+        for (int i = 0; i < comspec_len; i++)
+          SSET (entry, i, comspec[i]);
+    }
   }
 
   /* Remember the initial working directory for getcwd.  */
-- 
2.6.2.windows.1