Fix SH4 FP_ILOGB0 (bug 20859).

ISO C requires that the value of FP_ILOGB0 must be INT_MIN or
-INT_MAX.  In sysdeps/sh/sh4/bits/mathdef.h, it's 0x80000001; that is,
a positive unsigned value that would be -INT_MAX if converted to int,
which is not valid (there's no actual constraint on the type, but
whatever the type the integer value must be one of the two permitted,
and types other than int don't really make sense).  This patch makes
the ABI-compatible change to (-0x7fffffff).

(The testcase handles positive and negative sign separately to avoid
any issues with implicit conversions that could result in e.g. INT_MIN
converted to uintmax_t wrongly passing.)

Tested (compilation only) with build-many-glibcs.py.

	[BZ #20859]
	* sysdeps/sh/sh4/bits/mathdef.h (FP_ILOGB0): Define to
	(-0x7fffffff) instead of 0x80000001.
	* math/test-fp-ilogb-constants.c: New file.
	* math/Makefile (tests): Add test-fp-ilogb-constants.

4 files changed, 51 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 3063bd06af..b6fc831959 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2016-11-23  Joseph Myers  <joseph@codesourcery.com>
+
+	[BZ #20859]
+	* sysdeps/sh/sh4/bits/mathdef.h (FP_ILOGB0): Define to
+	(-0x7fffffff) instead of 0x80000001.
+	* math/test-fp-ilogb-constants.c: New file.
+	* math/Makefile (tests): Add test-fp-ilogb-constants.
+
 2016-11-23  Maciej W. Rozycki  <macro@imgtec.com>
 
 	* sysdeps/mips/mips32/crti.S (JALR_RELOC): New macro.
diff --git a/math/Makefile b/math/Makefile
index fe910ef6c0..e84f86ae2e 100644
--- a/math/Makefile
+++ b/math/Makefile
@@ -158,7 +158,8 @@ tests = test-matherr test-fenv atest-exp atest-sincos atest-exp2 basic-test \
 	test-fexcept test-fexcept-traps test-fesetexcept \
 	test-fesetexcept-traps test-fetestexceptflag test-femode \
 	test-femode-traps test-iszero-excess-precision \
-	test-iseqsig-excess-precision test-flt-eval-method $(tests-static)
+	test-iseqsig-excess-precision test-flt-eval-method \
+	test-fp-ilogb-constants $(tests-static)
 tests-static = test-fpucw-static test-fpucw-ieee-static \
 	       test-signgam-uchar-static test-signgam-uchar-init-static \
 	       test-signgam-uint-static test-signgam-uint-init-static \
diff --git a/math/test-fp-ilogb-constants.c b/math/test-fp-ilogb-constants.c
new file mode 100644
index 0000000000..eaa9cc1a02
--- /dev/null
+++ b/math/test-fp-ilogb-constants.c
@@ -0,0 +1,40 @@
+/* Test requirements on FP_ILOGB* constants.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <limits.h>
+#include <math.h>
+
+#if FP_ILOGB0 >= 0
+# error "FP_ILOGB0 is positive"
+#endif
+
+#if FP_ILOGB0 != INT_MIN && FP_ILOGB0 != -INT_MAX
+# error "FP_ILOGB0 must be INT_MIN or -INT_MAX"
+#endif
+
+#if FP_ILOGBNAN >= 0 && FP_ILOGBNAN != INT_MAX
+# error "FP_ILOGBNAN must be INT_MIN or INT_MAX"
+#endif
+
+#if FP_ILOGBNAN < 0 && FP_ILOGBNAN != INT_MIN
+# error "FP_ILOGBNAN must be INT_MIN or INT_MAX"
+#endif
+
+/* This is a compilation test.  */
+#define TEST_FUNCTION 0
+#include "../test-skeleton.c"
diff --git a/sysdeps/sh/sh4/bits/mathdef.h b/sysdeps/sh/sh4/bits/mathdef.h
index 90dbebb3fa..21ce094533 100644
--- a/sysdeps/sh/sh4/bits/mathdef.h
+++ b/sysdeps/sh/sh4/bits/mathdef.h
@@ -34,7 +34,7 @@ typedef float float_t;
 typedef double double_t;
 
 /* The values returned by `ilogb' for 0 and NaN respectively.  */
-# define FP_ILOGB0	0x80000001
+# define FP_ILOGB0	(-0x7fffffff)
 # define FP_ILOGBNAN	0x7fffffff
 
 #endif	/* ISO C99 */