logb: undeclared on Cygwin

[Bruno Haible]

Hi,

On Cygwin, the <math.h> function 'logb' is not declared, but is defined and
works.

  test-logb.c:24: error: `logb' undeclared here (not in a function)
  test-logb.c: In function `main':
  test-logb.c:38: warning: implicit declaration of function `logb'
  make[4]: *** [test-logb.o] Error 1

This works around the missing the declaration.


2010-03-07  Bruno Haible  <address@hidden>

        logb: Provide missing declaration for Cygwin.
        * lib/math.in.h (logb): New declaration.
        * m4/logb.m4: New file.
        * modules/logb (Files): Add m4/logb.m4.
        (Depends-on): Add math.
        (configure.ac): Invoke gl_FUNC_LOGB, gl_MATH_MODULE_INDICATOR.
        * m4/math_h.m4 (gl_MATH_H): Check also for logb declaration.
        (gl_MATH_H_DEFAULTS): Initialize GNULIB_LOGB, HAVE_DECL_LOGB.
        * modules/math (Makefile.am): Substitute GNULIB_LOGB, HAVE_DECL_LOGB.
        * doc/posix-functions/logb.texi: Mention the Cygwin bug.

================================= m4/logb.m4 =================================
# logb.m4 serial 1
dnl Copyright (C) 2010 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

AC_DEFUN([gl_FUNC_LOGB],
[
  AC_REQUIRE([gl_MATH_H_DEFAULTS])
  dnl Test whether logb() is declared.
  AC_CHECK_DECLS([logb], , , [#include <math.h>])
  if test "$ac_cv_have_decl_logb" != yes; then
    HAVE_DECL_LOGB=0
  fi
  dnl Test whether logb() can be used without libm.
  LOGB_LIBM=?
  AC_TRY_LINK([
     #ifndef __NO_MATH_INLINES
     # define __NO_MATH_INLINES 1 /* for glibc */
     #endif
     #include <math.h>
     extern double logb (double x);
     double x;],
    [x = logb(x);],
    [LOGB_LIBM=])
  if test "$LOGB_LIBM" = "?"; then
    save_LIBS="$LIBS"
    LIBS="$LIBS -lm"
    AC_TRY_LINK([
       #ifndef __NO_MATH_INLINES
       # define __NO_MATH_INLINES 1 /* for glibc */
       #endif
       #include <math.h>
       extern double logb (double x);
       double x;],
      [x = logb(x);],
      [LOGB_LIBM="-lm"])
    LIBS="$save_LIBS"
  fi
  if test "$LOGB_LIBM" = "?"; then
    LOGB_LIBM=
  fi
  AC_SUBST([LOGB_LIBM])
])
==============================================================================
--- doc/posix-functions/logb.texi.orig  Sun Mar  7 23:59:59 2010
+++ doc/posix-functions/logb.texi       Sun Mar  7 23:37:39 2010
@@ -12,4 +12,7 @@
 
 Portability problems not fixed by Gnulib:
 @itemize
address@hidden
+This function is missing a declaration on some platforms:
+Cygwin 1.5.x.
 @end itemize
--- lib/math.in.h.orig  Sun Mar  7 23:59:59 2010
+++ lib/math.in.h       Sun Mar  7 23:48:39 2010
@@ -97,6 +97,7 @@
 # define HUGE_VAL (1.0 / 0.0)
 #endif
 
+
 /* Write x as
      x = mantissa * 2^exp
    where
@@ -117,6 +118,19 @@
 #endif
 
 
+#if @GNULIB_LOGB@
+# if address@hidden@
+extern double logb (double x);
+# endif
+#elif defined GNULIB_POSIXCHECK
+# undef logb
+# if HAVE_RAW_DECL_LOGB
+_GL_WARN_ON_USE (logb, "logb is unportable - "
+                 "use gnulib module logb for portability");
+# endif
+#endif
+
+
 #if @GNULIB_ACOSL@
 # if address@hidden@ || address@hidden@
 extern long double acosl (long double x);
--- m4/math_h.m4.orig   Sun Mar  7 23:59:59 2010
+++ m4/math_h.m4        Sun Mar  7 23:49:09 2010
@@ -1,4 +1,4 @@
-# math_h.m4 serial 17
+# math_h.m4 serial 18
 dnl Copyright (C) 2007-2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -40,7 +40,7 @@
   dnl corresponding gnulib module is not in use.
   gl_WARN_ON_USE_PREPARE([[#include <math.h>
     ]], [acosl asinl atanl ceilf ceill cosl expl floorf floorl frexpl
-    ldexpl logl round roundf roundl sinl sqrtl tanl trunc truncf truncl])
+    ldexpl logb logl round roundf roundl sinl sqrtl tanl trunc truncf truncl])
 ])
 
 AC_DEFUN([gl_MATH_MODULE_INDICATOR],
@@ -70,6 +70,7 @@
   GNULIB_ISNAND=0;   AC_SUBST([GNULIB_ISNAND])
   GNULIB_ISNANL=0;   AC_SUBST([GNULIB_ISNANL])
   GNULIB_LDEXPL=0;   AC_SUBST([GNULIB_LDEXPL])
+  GNULIB_LOGB=0;     AC_SUBST([GNULIB_LOGB])
   GNULIB_LOGL=0;     AC_SUBST([GNULIB_LOGL])
   GNULIB_ROUND=0;    AC_SUBST([GNULIB_ROUND])
   GNULIB_ROUNDF=0;   AC_SUBST([GNULIB_ROUNDF])
@@ -101,6 +102,7 @@
   HAVE_DECL_EXPL=1;            AC_SUBST([HAVE_DECL_EXPL])
   HAVE_DECL_FREXPL=1;          AC_SUBST([HAVE_DECL_FREXPL])
   HAVE_DECL_LDEXPL=1;          AC_SUBST([HAVE_DECL_LDEXPL])
+  HAVE_DECL_LOGB=1;            AC_SUBST([HAVE_DECL_LOGB])
   HAVE_DECL_LOGL=1;            AC_SUBST([HAVE_DECL_LOGL])
   HAVE_DECL_SINL=1;            AC_SUBST([HAVE_DECL_SINL])
   HAVE_DECL_SQRTL=1;           AC_SUBST([HAVE_DECL_SQRTL])
--- modules/logb.orig   Sun Mar  7 23:59:59 2010
+++ modules/logb        Sun Mar  7 23:53:38 2010
@@ -2,12 +2,15 @@
 logb() function: get exponent.
 
 Files:
+m4/logb.m4
 m4/mathfunc.m4
 
 Depends-on:
+math
 
 configure.ac:
-gl_MATHFUNC([logb], [double], [(double)])
+gl_FUNC_LOGB
+gl_MATH_MODULE_INDICATOR([logb])
 
 Makefile.am:
 
--- modules/math.orig   Sun Mar  7 23:59:59 2010
+++ modules/math        Sun Mar  7 23:49:39 2010
@@ -42,6 +42,7 @@
              -e 's|@''GNULIB_ISNAND''@|$(GNULIB_ISNAND)|g' \
              -e 's|@''GNULIB_ISNANL''@|$(GNULIB_ISNANL)|g' \
              -e 's|@''GNULIB_LDEXPL''@|$(GNULIB_LDEXPL)|g' \
+             -e 's|@''GNULIB_LOGB''@|$(GNULIB_LOGB)|g' \
              -e 's|@''GNULIB_LOGL''@|$(GNULIB_LOGL)|g' \
              -e 's|@''GNULIB_ROUND''@|$(GNULIB_ROUND)|g' \
              -e 's|@''GNULIB_ROUNDF''@|$(GNULIB_ROUNDF)|g' \
@@ -72,6 +73,7 @@
              -e 's|@''HAVE_DECL_EXPL''@|$(HAVE_DECL_EXPL)|g' \
              -e 's|@''HAVE_DECL_FREXPL''@|$(HAVE_DECL_FREXPL)|g' \
              -e 's|@''HAVE_DECL_LDEXPL''@|$(HAVE_DECL_LDEXPL)|g' \
+             -e 's|@''HAVE_DECL_LOGB''@|$(HAVE_DECL_LOGB)|g' \
              -e 's|@''HAVE_DECL_LOGL''@|$(HAVE_DECL_LOGL)|g' \
              -e 's|@''HAVE_DECL_SINL''@|$(HAVE_DECL_SINL)|g' \
              -e 's|@''HAVE_DECL_SQRTL''@|$(HAVE_DECL_SQRTL)|g' \