clang-tidy - android-comparison-in-temp-failure-retry — Extra Clang Tools 13 documentation

# Extra Clang Tools 13 documentation

## clang-tidy - android-comparison-in-temp-failure-retry

# 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.
    }

## Options

RetryMacros

  A comma-separated list of the names of retry macros to be checked.