buildroot

From ccb15ee3d7e8c925cb3af9ea805feea2863c4f81 Mon Sep 17 00:00:00 2001

From: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Date: Fri, 1 May 2015 12:52:18 +0200

Subject: [PATCH] Link against libm when needed

​

In certain C libraries (e.g uClibc), isnan() and related functions are

implemented in libm, so json-c needs to link against it. This commit

therefore adds an AC_TRY_LINK() test to check whether a program

calling isnan() can be properly linked with no special flags. If not,

we assume linking against libm is needed.

​

The json-c.pc.in file is also adjusted so that in the case of static

linking against json-c, -lm is also used.

​

Submitted upstream: https://github.com/json-c/json-c/pull/182

​

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

---

 configure.ac | 4 ++++

 json-c.pc.in | 3 ++-

 2 files changed, 6 insertions(+), 1 deletion(-)

​

diff --git a/configure.ac b/configure.ac

index 99660a4..2a14ccf 100644

--- a/configure.ac

+++ b/configure.ac

@@ -50,6 +50,10 @@ AC_CHECK_DECLS([isinf], [], [], [[#include <math.h>]])

 AC_CHECK_DECLS([_isnan], [], [], [[#include <float.h>]])

 AC_CHECK_DECLS([_finite], [], [], [[#include <float.h>]])

+if test "$ac_cv_have_decl_isnan" = "yes" ; then

+   AC_TRY_LINK([#include <math.h>], [float f = 0.0; return isnan(f)], [], [LIBS="$LIBS -lm"])

+fi

+

 #check if .section.gnu.warning accepts long strings (for __warn_references)

 AC_LANG_PUSH([C])

diff --git a/json-c.pc.in b/json-c.pc.in

index 037739d..05bfbc8 100644

--- a/json-c.pc.in

+++ b/json-c.pc.in

@@ -6,6 +6,7 @@ includedir=@includedir@

 Name: json-c

 Description: JSON implementation in C

 Version: @VERSION@

-Requires: 

+Requires:

+Libs.private: @LIBS@

 Libs:  -L${libdir} -ljson-c

 Cflags: -I${includedir}/json-c

-- 

2.1.0

​