Define `_GNU_SOURCE` properly/consistently per autoconf

Although `_GNU_SOURCE` can be defined as an arbitrary #define per the
glibc docs [1], it's best to define it in a manner consistent with the way
that autoconf defines it, i.e., `1`.

While this shouldn't matter in most cases, it does when the headers from
other projects follow the poorly defined GNU convention implemented by
autoconf and are included after the libevent's util.h header. An example
failure with clang, similar to the failure I encountered, is as follows:
```
$ printf "#define _GNU_SOURCE\n#define _GNU_SOURCE 1" | clang -c -x c -
<stdin>:2:9: warning: '_GNU_SOURCE' macro redefined [-Wmacro-redefined]
        ^
<stdin>:1:9: note: previous definition is here
        ^
1 warning generated.
```

This happened when compiling python [2] with a stale homebrew util.h file from
libevent (which admittedly would not happen in a correct libevent install, as the
header should be installed under /usr/local/include/event2/util.h). However, if
both headers had been combined (which is more likely), it would have failed as
shown above.

Removing the ad hoc definition unbreaks compiling python's pyconfig.h.in header
when included after util.h from libevent.

1. http://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html
2. https://github.com/python/cpython/blob/master/configure.ac#L126

Closes: #773 (cherry-picked)
Signed-off-by: Enji Cooper <yaneurabeya@gmail.com>

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f847369a26c5c511901c2237bd9917be6881cb50..c761b04f3bb824753365a51be8545975faf93765 100644 (file)
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -334,7 +334,7 @@ if (NOT DEFINED _GNU_SOURCE)
 endif()
 
 if (_GNU_SOURCE)
-    add_definitions(-D_GNU_SOURCE)
+    add_definitions(-D_GNU_SOURCE=1)
 endif()
 
 CHECK_INCLUDE_FILE(sys/types.h EVENT__HAVE_SYS_TYPES_H)

diff --git a/configure.ac b/configure.ac
index 1889d6254425da66d02300746aeea44b35cdfa6b..e054b3a9a13e0b1eb664d6ff23c3ad037fd1143e 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -478,7 +478,7 @@ fi
 AC_MSG_CHECKING(for F_SETFD in fcntl.h)
 AC_EGREP_CPP(yes,
 [
-#define _GNU_SOURCE
+#define _GNU_SOURCE 1
 #include <fcntl.h>
 #ifdef F_SETFD
 yes
@@ -667,7 +667,7 @@ AC_CHECK_SIZEOF(off_t)
 AC_CHECK_SIZEOF(time_t)
 
 AC_CHECK_TYPES([struct in6_addr, struct sockaddr_in6, sa_family_t, struct addrinfo, struct sockaddr_storage], , ,
-[#define _GNU_SOURCE
+[#define _GNU_SOURCE 1
 #include <sys/types.h>
 #ifdef HAVE_NETINET_IN_H
 #include <netinet/in.h>

diff --git a/include/event2/util.h b/include/event2/util.h
index 7c872737656c3e771915e3b63aa47443f6be684b..e6df62899f165e0900b9ddae3992b2186bf18ea9 100644 (file)
--- a/include/event2/util.h
+++ b/include/event2/util.h
@@ -58,9 +58,6 @@ extern "C" {
 #endif
 #include <stdarg.h>
 #ifdef EVENT__HAVE_NETDB_H
-#if !defined(_GNU_SOURCE)
-#define _GNU_SOURCE
-#endif
 #include <netdb.h>
 #endif