Fix -Os log1p, log1pf build (bug 21314).

As reported in bug 21314, building log1p and log1pf fails with -Os
because of a spurious -Wmaybe-uninitialized warning (reported there
for GCC 5 for MIPS, I see it also with GCC 7 for x86_64).  This patch,
based on the patches in the bug, fixes this using the DIAG_* macros.

Tested for x86_64 with -Os that this eliminates those warnings and so
allows the build to progress further.

2018-02-01  Carlos O'Donell  <carlos@redhat.com>
	    Ramin Seyed-Moussavi  <lordrasmus@gmail.com>
	    Joseph Myers  <joseph@codesourcery.com>

	[BZ #21314]
	* sysdeps/ieee754/dbl-64/s_log1p.c: Include <libc-diag.h>.
	(__log1p): Disable -Wmaybe-uninitialized for -Os around
	computation using c.
	* sysdeps/ieee754/flt-32/s_log1pf.c: Include <libc-diag.h>.
	(__log1pf): Disable -Wmaybe-uninitialized for -Os around
	computation using c.

diff --git a/ChangeLog b/ChangeLog
index 585e69d43f873ccb09e21764ea5f7cadbf50888e..7923327a9d22513b5630e04ade5e164474d1033a 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,15 @@
+2018-02-01  Carlos O'Donell  <carlos@redhat.com>
+           Ramin Seyed-Moussavi  <lordrasmus@gmail.com>
+           Joseph Myers  <joseph@codesourcery.com>
+
+       [BZ #21314]
+       * sysdeps/ieee754/dbl-64/s_log1p.c: Include <libc-diag.h>.
+       (__log1p): Disable -Wmaybe-uninitialized for -Os around
+       computation using c.
+       * sysdeps/ieee754/flt-32/s_log1pf.c: Include <libc-diag.h>.
+       (__log1pf): Disable -Wmaybe-uninitialized for -Os around
+       computation using c.
+
 2018-02-01  Dmitry V. Levin  <ldv@altlinux.org>
 
        * version.h (RELEASE): Set to "development".

diff --git a/sysdeps/ieee754/dbl-64/s_log1p.c b/sysdeps/ieee754/dbl-64/s_log1p.c
index 340f6377f75f36b046382091314b9012848fdf61..b7cf5ce32149ec7bbd13e9acfc134442486fa437 100644 (file)
--- a/sysdeps/ieee754/dbl-64/s_log1p.c
+++ b/sysdeps/ieee754/dbl-64/s_log1p.c
@@ -81,6 +81,7 @@
 #include <float.h>
 #include <math.h>
 #include <math_private.h>
+#include <libc-diag.h>
 
 static const double
   ln2_hi = 6.93147180369123816490e-01,  /* 3fe62e42 fee00000 */
@@ -191,5 +192,14 @@ __log1p (double x)
   if (k == 0)
     return f - (hfsq - s * (hfsq + R));
   else
-    return k * ln2_hi - ((hfsq - (s * (hfsq + R) + (k * ln2_lo + c))) - f);
+    {
+      /* With GCC 7 when compiling with -Os the compiler warns that c
+        might be used uninitialized.  This can't be true because k
+        must be 0 for c to be uninitialized and we handled that
+        computation earlier without using c.  */
+      DIAG_PUSH_NEEDS_COMMENT;
+      DIAG_IGNORE_Os_NEEDS_COMMENT (7, "-Wmaybe-uninitialized");
+      return k * ln2_hi - ((hfsq - (s * (hfsq + R) + (k * ln2_lo + c))) - f);
+      DIAG_POP_NEEDS_COMMENT;
+    }
 }

diff --git a/sysdeps/ieee754/flt-32/s_log1pf.c b/sysdeps/ieee754/flt-32/s_log1pf.c
index ade60a2e27bb52c7ebb56559e37b3586eec49fa6..009084ee19e81601a64f1b42e7a8b01db57c9cba 100644 (file)
--- a/sysdeps/ieee754/flt-32/s_log1pf.c
+++ b/sysdeps/ieee754/flt-32/s_log1pf.c
@@ -16,6 +16,7 @@
 #include <float.h>
 #include <math.h>
 #include <math_private.h>
+#include <libc-diag.h>
 
 static const float
 ln2_hi =   6.9313812256e-01,   /* 0x3f317180 */
@@ -97,6 +98,18 @@ __log1pf(float x)
        s = f/((float)2.0+f);
        z = s*s;
        R = z*(Lp1+z*(Lp2+z*(Lp3+z*(Lp4+z*(Lp5+z*(Lp6+z*Lp7))))));
-       if(k==0) return f-(hfsq-s*(hfsq+R)); else
-                return k*ln2_hi-((hfsq-(s*(hfsq+R)+(k*ln2_lo+c)))-f);
+       if (k == 0)
+         return f - (hfsq - s * (hfsq + R));
+       else
+         {
+           /* With GCC 7 when compiling with -Os the compiler warns
+              that c might be used uninitialized.  This can't be true
+              because k must be 0 for c to be uninitialized and we
+              handled that computation earlier without using c.  */
+           DIAG_PUSH_NEEDS_COMMENT;
+           DIAG_IGNORE_Os_NEEDS_COMMENT (7, "-Wmaybe-uninitialized");
+           return k * ln2_hi - ((hfsq - (s * (hfsq + R)
+                                         + (k * ln2_lo + c))) - f);
+           DIAG_POP_NEEDS_COMMENT;
+         }
 }