Fix undefined args access for x86_64.
From libc manual for vsnprintf:
The functions vprintf(), vfprintf(), vsprintf(), vsnprintf()
are equivalent to the functions printf(), fprintf(), sprintf(), snprintf(),
respectively, except that they are called with a va_list instead of a
variable number of arguments. These functions do not call the va_end macro.
Because they invoke the va_arg macro, the value of ap is undefined after the call.
We need to allocate/end new va_list for each vsnprintf.
Change-Id: I66ec058033be1cb918e7b2bc84ca546800da226b
Signed-off-by: Fengwei Yin <fengwei.yin@intel.com>
diff --git a/libutils/String8.cpp b/libutils/String8.cpp
index e852d77..8acb4d4 100644
--- a/libutils/String8.cpp
+++ b/libutils/String8.cpp
@@ -323,8 +323,17 @@
status_t String8::appendFormatV(const char* fmt, va_list args)
{
- int result = NO_ERROR;
- int n = vsnprintf(NULL, 0, fmt, args);
+ int n, result = NO_ERROR;
+ va_list tmp_args;
+
+ /* args is undefined after vsnprintf.
+ * So we need a copy here to avoid the
+ * second vsnprintf access undefined args.
+ */
+ va_copy(tmp_args, args);
+ n = vsnprintf(NULL, 0, fmt, tmp_args);
+ va_end(tmp_args);
+
if (n != 0) {
size_t oldLength = length();
char* buf = lockBuffer(oldLength + n);