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 Sat, Nov 19, 2016 at 2:16 AM, Eli Zaretskii <eliz@gnu.org> wrote:
>
>   . I'd rather have the WINDOWSNT-specific code separate (on w32.c),
>     so perhaps the for-loop you modified could be left intact, and
>     instead we perform an additional pass over Vprocess_environment,
>     after it is already copied, to replace these two variables with
>     their upper-case equivalents, in that special code on w32.c.

Okay, here is a patch that does that.

>  . If you didn't already, please verify that these 2 variables in the
>    Emacs's own environment are also upcased, because otherwise I
>    think we will hit more such problems.

That would be the for loop just above my additions (I increased the
context so it's fully visible in the patch).

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From 1fe5e0dfb01a0400a90088d44f2f7fc2bd244a43 Mon Sep 17 00:00:00 2001
From: Noam Postavsky <npostavs@gmail.com>
Date: Fri, 18 Nov 2016 16:26:53 -0500
Subject: [PATCH v2] 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 | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/w32.c b/src/w32.c
index ad7d94a..0739e51 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -2867,10 +2867,28 @@ init_environment (char ** argv)
     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);
+
+    /* Make the same modification to `process-environment' which has
+       already been initialized in set_initial_environment.  */
+    Lisp_Object env = Vprocess_environment;
+    Lisp_Object path = build_string ("PATH=");
+    Lisp_Object path_len = make_number (SBYTES (path));
+    Lisp_Object comspec = build_string ("COMSPEC=");
+    Lisp_Object comspec_len = make_number (SBYTES (comspec));
+    for (; CONSP (env); env = XCDR (env))
+    {
+      Lisp_Object entry = XCAR (env);
+      if (EQ (Fcompare_strings (entry, Qnil, path_len, path, Qnil, Qnil, Qt), Qt))
+        for (ptrdiff_t i = 0; i < SBYTES (path); i++)
+          SSET (entry, i, SREF (path, i));
+      else if (EQ (Fcompare_strings (entry, Qnil, comspec_len, comspec, Qnil, Qnil, Qt), Qt))
+        for (ptrdiff_t i = 0; i < SBYTES (comspec); i++)
+          SSET (entry, i, SREF (comspec, i));
+    }
   }
 
   /* Remember the initial working directory for getcwd.  */
   /* FIXME: Do we need to resolve possible symlinks in startup_dir?
      Does it matter anywhere in Emacs?  */
-- 
2.6.2.windows.1