From d76cfec319760c71bf3d30b9960c9e666785c461 Mon Sep 17 00:00:00 2001
From: Jason Evans <jasone@canonware.com>
Date: Thu, 27 Oct 2016 21:23:48 -0700
Subject: [PATCH] Only link with libm (-lm) if necessary.

This fixes warnings when building with MSVC.
---
 Makefile.in  |  7 ++++---
 configure.ac | 15 ++++++++++++---
 2 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/Makefile.in b/Makefile.in
index eb77d9f2..e00dbebc 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -62,6 +62,7 @@ MKLIB = @MKLIB@
 AR = @AR@
 ARFLAGS = @ARFLAGS@
 CC_MM = @CC_MM@
+LM := @LM@
 INSTALL = @INSTALL@
 
 ifeq (macho, $(ABI))
@@ -300,15 +301,15 @@ $(STATIC_LIBS):
 
 $(objroot)test/unit/%$(EXE): $(objroot)test/unit/%.$(O) $(TESTS_UNIT_LINK_OBJS) $(C_JET_OBJS) $(C_TESTLIB_UNIT_OBJS)
 	@mkdir -p $(@D)
-	$(CC) $(LDTARGET) $(filter %.$(O),$^) $(call RPATH,$(objroot)lib) $(LDFLAGS) $(filter-out -lm,$(LIBS)) -lm $(EXTRA_LDFLAGS)
+	$(CC) $(LDTARGET) $(filter %.$(O),$^) $(call RPATH,$(objroot)lib) $(LDFLAGS) $(filter-out -lm,$(LIBS)) $(LM) $(EXTRA_LDFLAGS)
 
 $(objroot)test/integration/%$(EXE): $(objroot)test/integration/%.$(O) $(C_TESTLIB_INTEGRATION_OBJS) $(C_UTIL_INTEGRATION_OBJS) $(objroot)lib/$(LIBJEMALLOC).$(IMPORTLIB)
 	@mkdir -p $(@D)
-	$(CC) $(TEST_LD_MODE) $(LDTARGET) $(filter %.$(O),$^) $(call RPATH,$(objroot)lib) $(LJEMALLOC) $(LDFLAGS) $(filter-out -lm,$(filter -lrt -lpthread,$(LIBS))) -lm $(EXTRA_LDFLAGS)
+	$(CC) $(TEST_LD_MODE) $(LDTARGET) $(filter %.$(O),$^) $(call RPATH,$(objroot)lib) $(LJEMALLOC) $(LDFLAGS) $(filter-out -lm,$(filter -lrt -lpthread,$(LIBS))) $(LM) $(EXTRA_LDFLAGS)
 
 $(objroot)test/stress/%$(EXE): $(objroot)test/stress/%.$(O) $(C_JET_OBJS) $(C_TESTLIB_STRESS_OBJS) $(objroot)lib/$(LIBJEMALLOC).$(IMPORTLIB)
 	@mkdir -p $(@D)
-	$(CC) $(TEST_LD_MODE) $(LDTARGET) $(filter %.$(O),$^) $(call RPATH,$(objroot)lib) $(objroot)lib/$(LIBJEMALLOC).$(IMPORTLIB) $(LDFLAGS) $(filter-out -lm,$(LIBS)) -lm $(EXTRA_LDFLAGS)
+	$(CC) $(TEST_LD_MODE) $(LDTARGET) $(filter %.$(O),$^) $(call RPATH,$(objroot)lib) $(objroot)lib/$(LIBJEMALLOC).$(IMPORTLIB) $(LDFLAGS) $(filter-out -lm,$(LIBS)) $(LM) $(EXTRA_LDFLAGS)
 
 build_lib_shared: $(DSOS)
 build_lib_static: $(STATIC_LIBS)
diff --git a/configure.ac b/configure.ac
index f27c61f1..a9d75111 100644
--- a/configure.ac
+++ b/configure.ac
@@ -494,6 +494,15 @@ AC_SUBST([ARFLAGS])
 AC_SUBST([AROUT])
 AC_SUBST([CC_MM])
 
+dnl Determine whether libm must be linked to use e.g. log(3).
+AC_SEARCH_LIBS([log], [m], , [AC_MSG_ERROR([Missing math functions])])
+if test "x$ac_cv_search_log" != "xnone required" ; then
+  LM="$ac_cv_search_log"
+else
+  LM=
+fi
+AC_SUBST(LM)
+
 JE_COMPILABLE([__attribute__ syntax],
               [static __attribute__((unused)) void foo(void){}],
               [],
@@ -940,9 +949,9 @@ fi
 AC_MSG_CHECKING([configured backtracing method])
 AC_MSG_RESULT([$backtrace_method])
 if test "x$enable_prof" = "x1" ; then
-  if test "x$abi" != "xpecoff"; then
-    dnl Heap profiling uses the log(3) function.
-    LIBS="$LIBS -lm"
+  dnl Heap profiling uses the log(3) function.
+  if test "x$LM" != "x" ; then
+    LIBS="$LIBS $LM"
   fi
 
   AC_DEFINE([JEMALLOC_PROF], [ ])