From cee62ab20bf767c3a07562ad30c67126ea3bab32 Mon Sep 17 00:00:00 2001
From: Sergey Poznyakoff <gray@gnu.org>
Date: Sat, 20 Aug 2016 09:23:48 +0300
Subject: Fix environment modification code

Port fixes from GNU rush
---
 src/progman.c | 82 +++++++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 57 insertions(+), 25 deletions(-)

(limited to 'src')

diff --git a/src/progman.c b/src/progman.c
index fdb829a..43aff48 100644
--- a/src/progman.c
+++ b/src/progman.c
@@ -657,26 +657,48 @@ add_env (const char *name, const char *value)
   environ[i] = p;
 }
 
-static char *
-find_env (const char *name, int val)
+/* Find variable NAME in environment ENV.
+   On success, store the index of the ENV slot in *IDX,
+   the offset of the value (position right past '=') in *VALOFF, and
+   return 0 (IDX and/or VALOFF can be NULL, if that info is not needed).
+   Return -1 if NAME was not found. */
+static int
+find_env_pos (char **env, char *name, size_t *idx, size_t *valoff)
 {
-  if (environ)
-    {
-      int nlen = strcspn (name, "+=");
-      int i;
+  size_t nlen = strcspn (name, "+=");
+  size_t i;
 
-      for (i = 0; environ[i]; i++)
+  for (i = 0; env[i]; i++)
+    {
+      size_t elen = strcspn (env[i], "=");
+      if (elen == nlen && memcmp (name, env[i], nlen) == 0)
 	{
-	  size_t elen = strcspn (environ[i], "=");
-	  if (elen == nlen && memcmp (name, environ[i], nlen) == 0)
-	    return val ? environ[i] + elen + 1 : environ[i];
+	  if (idx)
+	    *idx = i;
+	  if (valoff)
+	    *valoff = elen + 1;
+	  return 0;
 	}
     }
-  return NULL;
+  return -1;
+}
+
+/* Find variable NAME in environment ENV.
+   On success, return pointer to the variable assignment (if VAL is 0),
+   or to the value (if VAL is 1).
+   Return NULL if NAME is not present in ENV. */
+static char *
+find_env_ptr (char **env, char *name, int val)
+{
+  size_t i, j;
+  if (find_env_pos (env, name, &i, &j))
+    return NULL;
+  return val ? env[i] + j : env[i];
 }
 
+/* Return 1 if ENV contains a matching unset statement for variable NAME. */
 static int
-locate_unset (char **env, const char *name)
+var_is_unset (char **env, const char *name)
 {
   int i;
   int nlen = strcspn (name, "=");
@@ -708,7 +730,7 @@ env_concat (const char *name, size_t namelen, const char *a, const char *b)
     {
       res = grecs_malloc (namelen + 1 + strlen (a) + strlen (b) + 1);
       strcpy (res + namelen + 1, a);
-      strcat (res, b);
+      strcat (res + namelen + 1, b);
     }
   else if (a)
     {
@@ -737,7 +759,7 @@ environ_setup (char **hint)
 {
   char **old_env = environ;
   char **new_env;
-  size_t count, i, n;
+  size_t count, i, j, n;
   
   if (!hint)
     return;
@@ -766,7 +788,7 @@ environ_setup (char **hint)
   if (old_env)
     for (i = 0; old_env[i]; i++)
       {
-	if (!locate_unset (hint, old_env[i]))
+	if (!var_is_unset (hint, old_env[i]))
 	  new_env[n++] = old_env[i];
       }
 
@@ -779,25 +801,35 @@ environ_setup (char **hint)
 	  /* Skip unset directives. */
 	  continue;
 	}
+
+      /* Find the slot for the variable.  Use next available
+	 slot if there's no such variable in new_env */
+      if (find_env_pos (new_env, hint[i], &j, NULL))
+	j = n;
+      
       if ((p = strchr (hint[i], '=')))
 	{
 	  if (p == hint[i])
 	    continue; /* Ignore erroneous entry */
 	  if (p[-1] == '+') 
-	    new_env[n++] = env_concat (hint[i], p - hint[i] - 1,
-				       find_env(hint[i], 1), p + 1);
+	    new_env[j] = env_concat (hint[i], p - hint[i] - 1,
+				     find_env_ptr (environ, hint[i], 1),
+				     p + 1);
 	  else if (p[1] == '+')
-	    new_env[n++] = env_concat (hint[i], p - hint[i],
-				       p + 2, find_env(hint[i], 1));
+	    new_env[j] = env_concat (hint[i], p - hint[i],
+				     p + 2,
+				     find_env_ptr (environ, hint[i], 1));
 	  else
-	    new_env[n++] = hint[i];
+	    new_env[j] = hint[i];
 	}
+      else if ((p = find_env_ptr (environ, hint[i], 0)))
+	new_env[j] = p;
       else
-	{
-	  p = find_env (hint[i], 0);
-	  if (p)
-	    new_env[n++] = p;
-	}
+	continue;
+
+      /* Adjust environment size */
+      if (j == n)
+	++n;
     }
   new_env[n] = NULL;
 
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