android-comparison-in-temp-failure-retry¶
Diagnoses comparisons that appear to be incorrectly placed in the argument to
the TEMP_FAILURE_RETRY macro. Having such a use is incorrect in the vast
majority of cases, and will often silently defeat the purpose of the
TEMP_FAILURE_RETRY macro.
For context, TEMP_FAILURE_RETRY is a convenience macro
provided by both glibc and Bionic. Its purpose is to repeatedly run a syscall
until it either succeeds, or fails for reasons other than being interrupted.
Example buggy usage looks like:
char cs[1];
while (TEMP_FAILURE_RETRY(read(STDIN_FILENO, cs, sizeof(cs)) != 0)) {
// Do something with cs.
}
Because TEMP_FAILURE_RETRY will check for whether the result of the comparison
is -1, and retry if so.
If you encounter this, the fix is simple: lift the comparison out of the
TEMP_FAILURE_RETRY argument, like so:
char cs[1];
while (TEMP_FAILURE_RETRY(read(STDIN_FILENO, cs, sizeof(cs))) != 0) {
// Do something with cs.
}