Commit fff9d11b authored Feb 27, 2014 by Fengwei Yin

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>

parent ebb46d76

libutils/String8.cpp

+11 −2

Original line number	Diff line number	Diff line
		@@ -323,8 +323,17 @@ status_t String8::appendFormat(const char* fmt, ...)

		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);