feature test macros: make _GNU_SOURCE enable everything

previously, a few BSD features were enabled only by _BSD_SOURCE, not
by _GNU_SOURCE. since _BSD_SOURCE is default in the absence of other
feature test macros, this made adding _GNU_SOURCE to a project not a
purely additive feature test macro; it actually caused some features
to be suppressed.

most of the changes made by this patch actually bring musl in closer
alignment with the glibc behavior for _GNU_SOURCE. the only exceptions
are the added visibility of functions like strlcpy which were BSD-only
due to being disliked/rejected by glibc maintainers. here, I feel the
consistency of having _GNU_SOURCE mean "everything", and especially
the property of it being purely additive, are more valuable than
hiding functions which glibc does not have.

1 files changed, 1 insertions, 1 deletions

diff --git a/include/signal.h b/include/signal.h
index 89080ab6..b24f43a5 100644
--- a/include/signal.h
+++ b/include/signal.h
@@ -212,7 +212,7 @@ void (*sigset(int, void (*)(int)))(int);
 #define NSIG _NSIG
 #endif
 
-#ifdef _BSD_SOURCE
+#if defined(_BSD_SOURCE) || defined(_GNU_SOURCE)
 typedef void (*sig_t)(int);
 #endif