[RFA] Environment variables passed to inferior by MinGW build (PR 10989)

[Eli Zaretskii <eliz@gnu.org>]

There's some history to this issue.  It was discussed at least twice
before:

   http://sourceware.org/ml/gdb-patches/2010-05/msg00317.html
   http://sourceware.org/ml/gdb-patches/2011-04/msg00347.html

The first discussion simply died because the OP never responded to
Joel's request to clean up the patch from weird characters.

As for the second discussion, upon re-reading it I can only assume
that there was a misunderstanding of some kind, perhaps Pierre was
talking about both the Cygwin and the native Windows builds, while
Chris and Corinna replied only about the latter.

In any case, the original problem is still there in the MinGW build of
GDB 7.3, and it just bit me hard enough to sit down and solve it.

The code in the patch below is simply taken from what was there before
it was deleted by Corinna back in 2006, after removing from it
everything that was Cygwin-specific.  So I don't even think I can take
credit for this code ;-)

With that patch, I can add environment variables with "set
environment", delete them with "unset environment", and the inferior
gets the environment I meant it to have.

OK to commit?

2011-09-11  Eli Zaretskii  <eliz@gnu.org>

	* windows-nat.c (env_sort) [!__CYGWIN__]: Function restored from
	before the change on 2006-12-09.
	(windows_create_inferior) [!__CYGWIN__]: Restore code that
	generates the environment block for CreateProcessA, modulo the
	Cygwin-specific parts that are not needed here.


=== modified file 'gdb/windows-nat.c'
--- gdb/windows-nat.c	2011-05-09 14:25:35 +0000
+++ gdb/windows-nat.c	2011-09-11 12:26:41 +0000
@@ -1951,6 +1951,17 @@
   *flags |= CREATE_NEW_CONSOLE;
 }
 
+#ifndef __CYGWIN__
+/* Function called by qsort to sort environment strings.  */
+static int
+env_sort (const void *a, const void *b)
+{
+  const char **p = (const char **) a;
+  const char **q = (const char **) b;
+  return strcasecmp (*p, *q);
+}
+#endif
+
 /* Start an inferior windows child process and sets inferior_ptid to its pid.
    EXEC_FILE is the file to run.
    ALLARGS is a string containing the arguments to the program.
@@ -1977,6 +1988,12 @@
   char *toexec;
   char *args;
   HANDLE tty;
+  char *w32env;
+  char *temp;
+  size_t envlen;
+  int i;
+  size_t envsize;
+  char **env;
 #endif
   PROCESS_INFORMATION pi;
   BOOL ret;
@@ -2124,6 +2141,31 @@
 	}
     }
 
+  /* CreateProcess takes the environment list as a null terminated set of
+     strings (i.e. two nulls terminate the list).  */
+
+  /* Get total size for env strings.  */
+  for (envlen = 0, i = 0; in_env[i] && *in_env[i]; i++)
+    envlen += strlen (in_env[i]) + 1;
+
+  envsize = sizeof (in_env[0]) * (i + 1);
+  env = (char **) alloca (envsize);
+  memcpy (env, in_env, envsize);
+  /* Windows programs expect the environment block to be sorted.  */
+  qsort (env, i, sizeof (char *), env_sort);
+
+  w32env = alloca (envlen + 1);
+
+  /* Copy env strings into new buffer.  */
+  for (temp = w32env, i = 0; env[i] && *env[i]; i++)
+    {
+      strcpy (temp, env[i]);
+      temp += strlen (temp) + 1;
+    }
+
+  /* Final nil string to terminate new env.  */
+  *temp = 0;
+
   windows_init_thread_list ();
   ret = CreateProcessA (0,
 			args,	/* command line */
@@ -2131,7 +2173,7 @@
 			NULL,	/* thread */
 			TRUE,	/* inherit handles */
 			flags,	/* start flags */
-			NULL,	/* environment */
+			w32env,	/* environment */
 			NULL,	/* current directory */
 			&si,
 			&pi);