[gnumeric] Configuration: add prototype for lgamma_r if headers fail to do so.

[Morten Welinder <mortenw src gnome org>]

commit 190590c7e1cdc5ab701a20650993572c9b40e1d0
Author: Morten Welinder <terra gnome org>
Date:   Thu Jun 20 21:09:21 2019 -0400

    Configuration: add prototype for lgamma_r if headers fail to do so.

 ChangeLog     |  6 ++++++
 NEWS          |  1 +
 configure.ac  | 19 +++++++++++++++++++
 src/numbers.h |  2 +-
 4 files changed, 27 insertions(+), 1 deletion(-)
---
diff --git a/ChangeLog b/ChangeLog
index 931e1cd15..41c71fff0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2019-06-20  Morten Welinder  <terra gnome org>
+
+       * configure.ac (lgamma_r): Check if we must prototype lgamma_r
+       ourselves.  Fixes #402.
+       * src/numbers.h: Do so, if needed.
+
 2019-06-09  Morten Welinder  <terra gnome org>
 
        * src/stf-parse.c (stf_parse_options_guess_formats): If we cannot
diff --git a/NEWS b/NEWS
index 7d3227f97..3492fa116 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,7 @@ Gnumeric 1.12.46
 
 Morten:
        * Fix over-eager guessing of dates in csv.  [#401]
+       * Fix Mac build problem.  [#402]
 
 --------------------------------------------------------------------------
 Gnumeric 1.12.45
diff --git a/configure.ac b/configure.ac
index a905c9676..129ebcca3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -739,6 +739,25 @@ if test "$GCC" = yes -a "x$set_more_warnings" != xno; then
 fi
 AC_SUBST(WARN_CFLAGS)
 
+if test "$ac_cv_func_lgamma_r" = yes -o "$ac_cv_lib_m_lgamma_r" = yes; then
+       AC_MSG_CHECKING([if we must prototype lgamma_r ourselves])
+       AC_RUN_IFELSE(
+               [AC_LANG_PROGRAM([[#include <math.h>
+#include <stdlib.h>]],
+                       [[
+                               const char *s = "-3.1415e+0";
+                               int sign;
+                               double res = lgamma_r (atof(s), &sign);
+                               return !(res >= 0.01630610 && res <= 0.01630611 && sign == +1);
+                       ]])],
+               [AC_MSG_RESULT(no)],
+               [AC_MSG_RESULT(yes)
+                AC_DEFINE([NEEDS_LGAMMA_R_PROTOTYPE], 1,
+                          [Define if we must prototype lgamma_r.])
+               ],
+               [AC_MSG_RESULT(assuming not)])
+fi
+
 dnl **************************************************
 dnl * Check for GSettings
 dnl **************************************************
diff --git a/src/numbers.h b/src/numbers.h
index 97b94cce5..e9128abfe 100644
--- a/src/numbers.h
+++ b/src/numbers.h
@@ -16,7 +16,7 @@ GO_VAR_DECL int signgam;
 double lgamma (double x);
 #endif
 
-#ifdef GNM_SUPPLIES_LGAMMA_R
+#if defined(GNM_SUPPLIES_LGAMMA_R) || defined(NEEDS_LGAMMA_R_PROTOTYPE)
 double lgamma_r (double x, int *signp);
 #endif