Reduce <limits.h> pollution due to dynamic PTHREAD_STACK_MIN

<limits.h> used to be a header file with no declarations.
GCC's libgomp includes it in a #pragma GCC visibility hidden block.
Including <unistd.h> from <limits.h> (indirectly) declares everything
in <unistd.h> with hidden visibility, resulting in linker failures.

This commit avoids C declarations in assembler mode and only declares
__sysconf in <limits.h> (and not the entire contents of <unistd.h>).
The __sysconf symbol is already part of the ABI.  PTHREAD_STACK_MIN
is no longer defined for __USE_DYNAMIC_STACK_SIZE && __ASSEMBLER__
because there is no possible definition.

Additionally, PTHREAD_STACK_MIN is now defined by <pthread.h> for
__USE_MISC because this is what developers expect based on the macro
name.  It also helps to avoid libgomp linker failures in GCC because
libgomp includes <pthread.h> before its visibility hacks.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/nptl/tst-minstack-exit.c b/nptl/tst-minstack-exit.c
index 4e7dc3e786..e577924178 100644
--- a/nptl/tst-minstack-exit.c
+++ b/nptl/tst-minstack-exit.c
@@ -24,6 +24,9 @@
 #include <support/check.h>
 #include <support/xthread.h>
 
+_Static_assert (__SC_THREAD_STACK_MIN_VALUE == _SC_THREAD_STACK_MIN,
+                "__SC_THREAD_STACK_MIN_VALUE is correct");
+
 static void *
 threadfunc (void *closure)
 {