Re: new module 'frexpf'

[Bruno Haible]

On IRIX 6.5 and mingw, the system function frexpf() has some of the bugs
that the frexp() also has. Here's the workaround:


2011-10-06  Bruno Haible  <address@hidden>

        frexpf: Work around problems on IRIX and mingw.
        * lib/math.in.h (frexpf): Consider also REPLACE_FREXPF.
        * m4/math_h.m4 (gl_MATH_H_DEFAULTS): Initialize REPLACE_FREXPF.
        * m4/frexpf.m4 (gl_FUNC_FREXPF_WORKS): New macro.
        (gl_FUNC_FREXPF): Invoke it. Set REPLACE_FREXPF.
        * modules/frexpf (Depends-on, configure.ac): Consider REPLACE_FREXPF.
        * modules/math (Makefile.am): Substitute REPLACE_FREXPF.
        * doc/posix-functions/frexpf.texi: Mention the IRIX and mingw problems.

--- doc/posix-functions/frexpf.texi.orig        Fri Oct  7 00:58:44 2011
+++ doc/posix-functions/frexpf.texi     Thu Oct  6 22:46:47 2011
@@ -10,10 +10,16 @@
 @itemize
 @item
 This function is missing on some platforms:
-Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, Solaris 9.
+Minix 3.1.8, AIX 5.1, HP-UX 11, Solaris 9.
 @item
 This function is only defined as a macro with arguments on some platforms:
 MSVC 9.
address@hidden
+This function does not work on negative zero on some platforms:
+mingw.
address@hidden
+This function does not work on infinite numbers on some platforms:
+IRIX 6.5, mingw.
 @end itemize
 
 Portability problems not fixed by Gnulib:
--- lib/math.in.h.orig  Fri Oct  7 00:58:44 2011
+++ lib/math.in.h       Fri Oct  7 00:28:01 2011
@@ -343,11 +343,20 @@
      If x is infinite or NaN: mantissa = x, exp unspecified.
    Store exp in *EXPPTR and return mantissa.  */
 #if @GNULIB_FREXPF@
-# if address@hidden@
-#  undef frexpf
+# if @REPLACE_FREXPF@
+#  if !(defined __cplusplus && defined GNULIB_NAMESPACE)
+#   undef frexpf
+#   define frexpf rpl_frexpf
+#  endif
+_GL_FUNCDECL_RPL (frexpf, float, (float x, int *expptr) _GL_ARG_NONNULL ((2)));
+_GL_CXXALIAS_RPL (frexpf, float, (float x, int *expptr));
+# else
+#  if address@hidden@
+#   undef frexpf
 _GL_FUNCDECL_SYS (frexpf, float, (float x, int *expptr) _GL_ARG_NONNULL ((2)));
-# endif
+#  endif
 _GL_CXXALIAS_SYS (frexpf, float, (float x, int *expptr));
+# endif
 _GL_CXXALIASWARN (frexpf);
 #elif defined GNULIB_POSIXCHECK
 # undef frexpf
--- m4/frexpf.m4.orig   Fri Oct  7 00:58:44 2011
+++ m4/frexpf.m4        Fri Oct  7 00:56:43 2011
@@ -1,4 +1,4 @@
-# frexpf.m4 serial 2
+# frexpf.m4 serial 3
 dnl Copyright (C) 2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -13,10 +13,81 @@
   dnl exists, is defined in the same library as frexp(). This is not the case
   dnl on NetBSD, OpenBSD.
   gl_MATHFUNC([frexpf], [float], [(float, int *)])
-  if test $gl_cv_func_frexpf_no_libm = no \
-     && test $gl_cv_func_frexpf_in_libm = no; then
+  if test $gl_cv_func_frexpf_no_libm = yes \
+     || test $gl_cv_func_frexpf_in_libm = yes; then
+    save_LIBS="$LIBS"
+    LIBS="$LIBS $FREXPF_LIBM"
+    gl_FUNC_FREXPF_WORKS
+    LIBS="$save_LIBS"
+    case "$gl_cv_func_frexpf_works" in
+      *yes) ;;
+      *)    REPLACE_FREXPF=1 ;;
+    esac
+  else
     HAVE_FREXPF=0
+  fi
+  if test $HAVE_FREXPF = 0 || test $REPLACE_FREXPF = 1; then
     FREXPF_LIBM="$FREXP_LIBM"
   fi
   AC_SUBST([FREXPF_LIBM])
 ])
+
+dnl Test whether frexpf() works also on infinite numbers (this fails e.g. on
+dnl IRIX 6.5 and mingw) and on negative zero (this fails e.g. on mingw).
+AC_DEFUN([gl_FUNC_FREXPF_WORKS],
+[
+  AC_REQUIRE([AC_PROG_CC])
+  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+  AC_CACHE_CHECK([whether frexpf works], [gl_cv_func_frexpf_works],
+    [
+      AC_RUN_IFELSE(
+        [AC_LANG_SOURCE([[
+#include <float.h>
+#include <math.h>
+#include <string.h>
+/* HP cc on HP-UX 10.20 has a bug with the constant expression -0.0.
+   ICC 10.0 has a bug when optimizing the expression -zero.
+   The expression -FLT_MIN * FLT_MIN does not work when cross-compiling
+   to PowerPC on MacOS X 10.5.  */
+#if defined __hpux || defined __sgi || defined __ICC
+static float
+compute_minus_zero (void)
+{
+  return -FLT_MIN * FLT_MIN;
+}
+# define minus_zero compute_minus_zero ()
+#else
+float minus_zero = -0.0f;
+#endif
+int main()
+{
+  int result = 0;
+  volatile float x;
+  float zero = 0.0f;
+  /* Test on infinite numbers.  */
+  x = 1.0f / zero;
+  {
+    int exp;
+    float y = frexpf (x, &exp);
+    if (y != x)
+      result |= 1;
+  }
+  /* Test on negative zero.  */
+  x = minus_zero;
+  {
+    int exp;
+    float y = frexpf (x, &exp);
+    if (memcmp (&y, &x, sizeof x))
+      result |= 2;
+  }
+  return result;
+}]])],
+        [gl_cv_func_frexpf_works=yes],
+        [gl_cv_func_frexpf_works=no],
+        [case "$host_os" in
+           irix* | mingw*) gl_cv_func_frexpf_works="guessing no";;
+           *)              gl_cv_func_frexpf_works="guessing yes";;
+         esac
+        ])
+    ])
+])
--- m4/math_h.m4.orig   Fri Oct  7 00:58:44 2011
+++ m4/math_h.m4        Fri Oct  7 00:28:40 2011
@@ -1,4 +1,4 @@
-# math_h.m4 serial 29
+# math_h.m4 serial 30
 dnl Copyright (C) 2007-2011 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -137,6 +137,7 @@
   REPLACE_FLOOR=0;             AC_SUBST([REPLACE_FLOOR])
   REPLACE_FLOORF=0;            AC_SUBST([REPLACE_FLOORF])
   REPLACE_FLOORL=0;            AC_SUBST([REPLACE_FLOORL])
+  REPLACE_FREXPF=0;            AC_SUBST([REPLACE_FREXPF])
   REPLACE_FREXP=0;             AC_SUBST([REPLACE_FREXP])
   REPLACE_FREXPL=0;            AC_SUBST([REPLACE_FREXPL])
   REPLACE_HUGE_VAL=0;          AC_SUBST([REPLACE_HUGE_VAL])
--- modules/frexpf.orig Fri Oct  7 00:58:44 2011
+++ modules/frexpf      Fri Oct  7 00:30:12 2011
@@ -8,11 +8,11 @@
 
 Depends-on:
 math
-frexp           [test $HAVE_FREXPF = 0]
+frexp           [test $HAVE_FREXPF = 0 || test $REPLACE_FREXPF = 1]
 
 configure.ac:
 gl_FUNC_FREXPF
-if test $HAVE_FREXPF = 0; then
+if test $HAVE_FREXPF = 0 || test $REPLACE_FREXPF = 1; then
   AC_LIBOBJ([frexpf])
 fi
 gl_MATH_MODULE_INDICATOR([frexpf])
--- modules/math.orig   Fri Oct  7 00:58:44 2011
+++ modules/math        Fri Oct  7 00:29:02 2011
@@ -110,6 +110,7 @@
              -e 's|@''REPLACE_FLOOR''@|$(REPLACE_FLOOR)|g' \
              -e 's|@''REPLACE_FLOORF''@|$(REPLACE_FLOORF)|g' \
              -e 's|@''REPLACE_FLOORL''@|$(REPLACE_FLOORL)|g' \
+             -e 's|@''REPLACE_FREXPF''@|$(REPLACE_FREXPF)|g' \
              -e 's|@''REPLACE_FREXP''@|$(REPLACE_FREXP)|g' \
              -e 's|@''REPLACE_FREXPL''@|$(REPLACE_FREXPL)|g' \
              -e 's|@''REPLACE_HUGE_VAL''@|$(REPLACE_HUGE_VAL)|g' \

-- 
In memoriam Bahriye Üçok <http://en.wikipedia.org/wiki/Bahriye_Üçok>