From b6943186ce78105155ba67ab261a970859b190df Mon Sep 17 00:00:00 2001
From: Elliott Hughes <enh@google.com>
Date: Tue, 13 May 2014 10:14:22 -0700
Subject: [PATCH] Reduce stack usage of tmpfile(3).

Also ensure that none of our home-grown code uses more than 2KiB per frame.

Change-Id: I8987a17d72f4b7f082bb7fa25e137c8433664c14
---
 libc/Android.mk         |  5 ++++-
 libc/bionic/tmpfile.cpp | 11 ++++++-----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/libc/Android.mk b/libc/Android.mk
index 2ec12811c..b5a808854 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -727,7 +727,10 @@ include $(BUILD_STATIC_LIBRARY)
 include $(CLEAR_VARS)
 
 LOCAL_SRC_FILES := $(libc_bionic_src_files)
-LOCAL_CFLAGS := $(libc_common_cflags) -Werror
+LOCAL_CFLAGS := $(libc_common_cflags) \
+    -Werror \
+    -Wframe-larger-than=2048 \
+
 LOCAL_CONLYFLAGS := $(libc_common_conlyflags)
 LOCAL_CPPFLAGS := $(libc_common_cppflags)
 LOCAL_C_INCLUDES := $(libc_common_c_includes)
diff --git a/libc/bionic/tmpfile.cpp b/libc/bionic/tmpfile.cpp
index 8419ff529..602d40752 100644
--- a/libc/bionic/tmpfile.cpp
+++ b/libc/bionic/tmpfile.cpp
@@ -57,22 +57,23 @@ class ScopedSignalBlocker {
 };
 
 static FILE* __tmpfile_dir(const char* tmp_dir) {
-  char buf[PATH_MAX];
-  int path_length = snprintf(buf, sizeof(buf), "%s/tmp.XXXXXXXXXX", tmp_dir);
-  if (path_length >= static_cast<int>(sizeof(buf))) {
+  char* path = NULL;
+  if (asprintf(&path, "%s/tmp.XXXXXXXXXX", tmp_dir) == -1) {
     return NULL;
   }
 
   int fd;
   {
     ScopedSignalBlocker ssb;
-    fd = mkstemp(buf);
+    fd = mkstemp(path);
     if (fd == -1) {
+      free(path);
       return NULL;
     }
 
     // Unlink the file now so that it's removed when closed.
-    unlink(buf);
+    unlink(path);
+    free(path);
 
     // Can we still use the file now it's unlinked?
     // File systems without hard link support won't have the usual Unix semantics.