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[patch] valprint.c (read_string): Rework clean-up logic.
- From: Phil Muldoon <pmuldoon at redhat dot com>
- To: gdb-patches at sourceware dot org
- Date: Fri, 27 Feb 2009 18:22:20 +0000
- Subject: [patch] valprint.c (read_string): Rework clean-up logic.
Hi,
While performing some Valgrind profiling on GDB we found that the
"read_string" function in valprint.c can leak clean-ups. This happens
as it does not account for a previous clean-up in the local chain and
overwrites the local "old_chain" place holder with a new one. This patch
reworks the function's clean-up logic, only registering one clean-up at
the beginning and including a new clean-up function. This new clean-up
function frees buffers referenced by double indirection.
This patch neither increases or decreases regressions in the test-suite.
It was built and tested on X86_64.
2009-02-27 Phil Muldoon <pmuldoon@redhat.com>
* valprint.c (xfree_gdb_byte): New function.
(read_string): Rework clean-up logic. Use xfree_gdb_byte for
clean-up.
Index: gdb/valprint.c
===================================================================
RCS file: /cvs/src/src/gdb/valprint.c,v
retrieving revision 1.79
diff -u -r1.79 valprint.c
--- gdb/valprint.c 5 Feb 2009 12:16:25 -0000 1.79
+++ gdb/valprint.c 27 Feb 2009 17:55:46 -0000
@@ -1177,6 +1177,15 @@
return (nread);
}
+/* Local clean-up for a gdb_byte buffer pointed to via double
+ indirection. This function is used in read_string. */
+static void
+xfree_gdb_byte (void *buffer)
+{
+ gdb_byte **pointer = buffer;
+ xfree (*pointer);
+}
+
/* Read a string from the inferior, at ADDR, with LEN characters of WIDTH bytes
each. Fetch at most FETCHLIMIT characters. BUFFER will be set to a newly
allocated buffer containing the string, which the caller is responsible to
@@ -1226,13 +1235,14 @@
some error, such as bumping into the end of the address space. */
found_nul = 0;
- old_chain = make_cleanup (null_cleanup, 0);
+ *buffer = NULL;
+
+ old_chain = make_cleanup (xfree_gdb_byte, buffer);
if (len > 0)
{
*buffer = (gdb_byte *) xmalloc (len * width);
bufptr = *buffer;
- old_chain = make_cleanup (xfree, *buffer);
nfetch = partial_memory_read (addr, bufptr, len * width, &errcode)
/ width;
@@ -1243,8 +1253,6 @@
{
unsigned long bufsize = 0;
- *buffer = NULL;
-
do
{
QUIT;
@@ -1253,13 +1261,9 @@
if (*buffer == NULL)
*buffer = (gdb_byte *) xmalloc (nfetch * width);
else
- {
- discard_cleanups (old_chain);
- *buffer = (gdb_byte *) xrealloc (*buffer,
- (nfetch + bufsize) * width);
- }
+ *buffer = (gdb_byte *) xrealloc (*buffer,
+ (nfetch + bufsize) * width);
- old_chain = make_cleanup (xfree, *buffer);
bufptr = *buffer + bufsize * width;
bufsize += nfetch;