Fix finite-math-only lgamma functions signgam setting (bug 19211).

The lgamma inline functions in bits/math-finite.h do not set signgam
if __USE_ISOC99, even when other feature test macros mean a standard
such as XSI POSIX is selected for which it should be set.  (This is
essentially the opposite issue to bug 15421, the out-of-line versions
setting signgam even when they shouldn't.)

This patch fixes those functions to use __USE_MISC || __USE_XOPEN as
the condition for when to set signgam, since it's the condition for
when math.h declares signgam.  The legacy gamma* names are only
declared at all if __USE_MISC || __USE_XOPEN, so they just set signgam
unconditionally.

Tests for certain standards or not using _GNU_SOURCE cannot use
test-skeleton.c (this is a known issue noted on the wiki todo list).
Thus, the new tests that signgam remains not set in ISO C modes do not
use test-skeleton.c.  They also define _ISOMAC to avoid running into
declarations in the internal include/ headers that only work in
_GNU_SOURCE mode.

Tested for x86_64 and x86.

	[BZ #19211]
	* math/bits/math-finite.h (lgamma): Set signgam if [__USE_MISC ||
	__USE_XOPEN], not if [!__USE_ISOC99].
	(lgammaf): Likewise.
	(lgammal): Likewise.
	(gamma): Set signgam unconditionally, not if [!__USE_ISOC99].
	(gammaf): Likewise.
	(gammal): Likewise.
	* math/test-signgam-finite-c11.c: New file.
	* math/test-signgam-finite-c99.c: Likewise.
	* math/test-signgam-finite.c: Likewise.
	* math/Makefile (tests): Add test-signgam-finite,
	test-signgam-finite-c99 and test-signgam-finite-c11.
	(CFLAGS-test-signgam-finite.c): New variable.
	(CFLAGS-test-signgam-finite-c99.c): Likewise.
	(CFLAGS-test-signgam-finite-c11.c): Likewise.

1 files changed, 6 insertions, 1 deletions

diff --git a/math/Makefile b/math/Makefile
index 3efbc58d5c..adeb806e3f 100644
--- a/math/Makefile
+++ b/math/Makefile
@@ -108,7 +108,8 @@ tests = test-matherr test-fenv atest-exp atest-sincos atest-exp2 basic-test \
 	test-tgmath-ret bug-nextafter bug-nexttoward bug-tgmath1 \
 	test-tgmath-int test-tgmath2 test-powl tst-CMPLX tst-CMPLX2 test-snan \
 	test-fenv-tls test-fenv-preserve test-fenv-return test-fenvinline \
-	test-nearbyint-except test-fenv-clear $(tests-static)
+	test-nearbyint-except test-fenv-clear test-signgam-finite \
+	test-signgam-finite-c99 test-signgam-finite-c11 $(tests-static)
 tests-static = test-fpucw-static test-fpucw-ieee-static
 # We do the `long double' tests only if this data type is available and
 # distinct from `double'.
@@ -185,6 +186,10 @@ CPPFLAGS-test-idouble.c = -U__LIBC_INTERNAL_MATH_INLINES \
 CPPFLAGS-test-ildoubl.c = -U__LIBC_INTERNAL_MATH_INLINES \
 			  $(libm-test-fast-math-cflags)
 
+CFLAGS-test-signgam-finite.c = -ffinite-math-only
+CFLAGS-test-signgam-finite-c99.c = -ffinite-math-only -std=c99
+CFLAGS-test-signgam-finite-c11.c = -ffinite-math-only -std=c11
+
 # The -lieee module sets the _LIB_VERSION_ switch to IEEE mode
 # for error handling in the -lm functions.
 install-lib += libieee.a