1.. title:: clang-tidy - android-comparison-in-temp-failure-retry
2
3android-comparison-in-temp-failure-retry
4========================================
5
6Diagnoses comparisons that appear to be incorrectly placed in the argument to
7the ``TEMP_FAILURE_RETRY`` macro. Having such a use is incorrect in the vast
8majority of cases, and will often silently defeat the purpose of the
9``TEMP_FAILURE_RETRY`` macro.
10
11For context, ``TEMP_FAILURE_RETRY`` is `a convenience macro
12<https://www.gnu.org/software/libc/manual/html_node/Interrupted-Primitives.html>`_
13provided by both glibc and Bionic. Its purpose is to repeatedly run a syscall
14until it either succeeds, or fails for reasons other than being interrupted.
15
16Example buggy usage looks like:
17
18.. code-block:: c
19
20  char cs[1];
21  while (TEMP_FAILURE_RETRY(read(STDIN_FILENO, cs, sizeof(cs)) != 0)) {
22    // Do something with cs.
23  }
24
25Because TEMP_FAILURE_RETRY will check for whether the result *of the comparison*
26is ``-1``, and retry if so.
27
28If you encounter this, the fix is simple: lift the comparison out of the
29``TEMP_FAILURE_RETRY`` argument, like so:
30
31.. code-block:: c
32
33  char cs[1];
34  while (TEMP_FAILURE_RETRY(read(STDIN_FILENO, cs, sizeof(cs))) != 0) {
35    // Do something with cs.
36  }
37
38Options
39-------
40
41.. option:: RetryMacros
42
43   A comma-separated list of the names of retry macros to be checked.
44