Replace readlink calls with a safer version that guarantees NULL-termination.

This patch is part of a bigger patch that helps merging the breakpad code
with the modified version in Chromium OS.

Specifically, this patch makes the following changes:
1. Add a SafeReadLink function that wraps sys_readlink() to resolve a
   symbolic link but guarantees the result is NULL-terminated on success.
2. Refactor other source code to use SafeReadLink instead of readlink()
   or sys_readlink().

BUG=455
TEST=Tested the following:
1. Build on 32-bit and 64-bit Linux with gcc 4.4.3 and gcc 4.6.
2. Build on Mac OS X 10.6.8 with gcc 4.2 and clang 3.0 (with latest gmock).
3. All unit tests pass.
4. Run minidump-2-core to covnert a minidump file to a core file.
Review URL: http://breakpad.appspot.com/334001

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@896 4c0a9323-5329-0410-9bdc-e9ce6186880e

1 files changed, 3 insertions, 2 deletions

diff --git a/src/client/linux/minidump_writer/minidump_writer_unittest.cc b/src/client/linux/minidump_writer/minidump_writer_unittest.cc
index 41465268..ee021ae3 100644
--- a/src/client/linux/minidump_writer/minidump_writer_unittest.cc
+++ b/src/client/linux/minidump_writer/minidump_writer_unittest.cc
@@ -42,6 +42,7 @@
 #include "client/linux/minidump_writer/minidump_writer.h"
 #include "common/linux/eintr_wrapper.h"
 #include "common/linux/file_id.h"
+#include "common/linux/safe_readlink.h"
 #include "common/tests/auto_tempdir.h"
 #include "google_breakpad/processor/minidump.h"
 
@@ -287,8 +288,8 @@ TEST(MinidumpWriterTest, DeletedBinary) {
 
   // Locate helper binary next to the current binary.
   char self_path[PATH_MAX];
-  if (readlink("/proc/self/exe", self_path, sizeof(self_path) - 1) == -1) {
-    FAIL() << "readlink failed: " << strerror(errno);
+  if (!SafeReadLink("/proc/self/exe", self_path)) {
+    FAIL() << "readlink failed";
     exit(1);
   }
   string helper_path(self_path);