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Enable _GNU_SOURCE for Android

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When targeting the Android NDK _GNU_SOURCE is not enabled by default:

```
 /*
  * With bionic, you always get all C and POSIX API.
  *
  * If you want BSD and/or GNU extensions, _BSD_SOURCE and/or _GNU_SOURCE are
  * expected to be defined by callers before *any* standard header file is
  * included.
  *
  * In our header files we test against __USE_BSD and __USE_GNU.
  */
 #if defined(_GNU_SOURCE)
 #  define __USE_BSD 1
 #  define __USE_GNU 1
 #endif
```

Because of this `pipe2` is not available:

```
 #if defined(__USE_GNU)
 int pipe2(int __fds[2], int __flags) __INTRODUCED_IN(9);
 #endif
```

The function used to check if it does exist:

```
CHECK_FUNCTION_EXISTS_EX(pipe2 EVENT__HAVE_PIPE2)
```

Just check that the _linking_ succeeds, which it does, it's just not
visible in the import, leading to a warning (or error):

```
evutil.c:2637:6: error: implicit declaration of function 'pipe2' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        if (pipe2(fd, O_NONBLOCK|O_CLOEXEC) == 0)
            ^
```

When targeting the NDK it should be safe to always opt into this. Clang
would pass the right flag for us automatically _if_ the source was C++
instead of C.

(cherry picked from commit 41c95abb9930b0c13c238e110b857acb810ad7b9)
This commit is contained in:
Keith Smiley 2019-07-08 14:06:55 -07:00 committed by Azat Khuzhin
parent 3aa68a82dc
commit f013fc7dde
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1 changed files with 4 additions and 0 deletions
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4
CMakeLists.txt
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@ -337,6 +337,10 @@ if (NOT DEFINED _GNU_SOURCE)
unset(_GNU_SOURCE CACHE) unset(_GNU_SOURCE CACHE)
CHECK_SYMBOL_EXISTS(_GNU_SOURCE "features.h" _GNU_SOURCE) CHECK_SYMBOL_EXISTS(_GNU_SOURCE "features.h" _GNU_SOURCE)
endif() endif()
if (ANDROID)
set(_GNU_SOURCE TRUE)
endif()
endif() endif()
if (_GNU_SOURCE) if (_GNU_SOURCE)