2011-08-29  Paul Smith  <psmith@gnu.org>

	* expand.c (variable_expand_string): Always allocate a new buffer

	for a string we're expanding.  The string we're working on can get

	freed while we work on it (for example if it's the value of a

	variable which modifies itself using an eval operation).

	See Savannah patch #7534 for the original report by Lubomir Rintel.

	* tests/scripts/features/varnesting: Test resetting of variables while

	expanding them.  See Savannah patch #7534

--- a/expand.c

+++ b/expand.c

@@ -197,7 +197,7 @@ variable_expand_string (char *line, const char *string, long length)

 {

   struct variable *v;

   const char *p, *p1;

-  char *abuf = NULL;

+  char *save;

   char *o;

   unsigned int line_offset;

@@ -212,16 +212,11 @@ variable_expand_string (char *line, const char *string, long length)

       return (variable_buffer);

     }

-  /* If we want a subset of the string, allocate a temporary buffer for it.

-     Most of the functions we use here don't work with length limits.  */

-  if (length > 0 && string[length] != '\0')

-    {

-      abuf = xmalloc(length+1);

-      memcpy(abuf, string, length);

-      abuf[length] = '\0';

-      string = abuf;

-    }

-  p = string;

+  /* We need a copy of STRING: due to eval, it's possible that it will get

+     freed as we process it (it might be the value of a variable that's reset

+     for example).  Also having a nil-terminated string is handy.  */

+  save = length < 0 ? xstrdup (string) : xstrndup (string, length);

+  p = save;

   while (1)

     {

@@ -411,8 +406,7 @@ variable_expand_string (char *line, const char *string, long length)

       ++p;

     }

-  if (abuf)

-    free (abuf);

+  free (save);

   variable_buffer_output (o, "", 1);

   return (variable_buffer + line_offset);

--- a/tests/scripts/features/varnesting

+++ b/tests/scripts/features/varnesting

@@ -1,29 +1,30 @@

-$description = "The following test creates a makefile to ...";

+#                                                                    -*-perl-*-

+$description = "Test recursive variables";

 $details = "";

-open(MAKEFILE,"> $makefile");

-

-# The Contents of the MAKEFILE ...

-

-print MAKEFILE "x = variable1\n"

-              ."variable2 := Hello\n"

-              ."y = \$(subst 1,2,\$(x))\n"

-              ."z = y\n"

-              ."a := \$(\$(\$(z)))\n"

-              ."all: \n"

-              ."\t\@echo \$(a)\n";

-

-# END of Contents of MAKEFILE

-

-close(MAKEFILE);

-

-&run_make_with_options($makefile,"",&get_logfile);

-

-# Create the answer to what should be produced by this Makefile

-$answer = "Hello\n";

-

-&compare_output($answer,&get_logfile(1));

+run_make_test('

+x = variable1

+variable2 := Hello

+y = $(subst 1,2,$(x))

+z = y

+a := $($($(z)))

+all: 

+	@echo $(a)

+',

+              '', "Hello\n");

+

+# This tests resetting the value of a variable while expanding it.

+# You may only see problems with this if you're using valgrind or

+# some other memory checker that poisons freed memory.

+# See Savannah patch #7534

+

+run_make_test('

+VARIABLE = $(eval VARIABLE := echo hi)$(VARIABLE)

+wololo:

+	@$(VARIABLE)

+',

+              '', "hi\n");

 1;