Use -fvisibility=hidden to build libm.

Bug: 11156955
Change-Id: I77b7772a44313a1eb3970f5d2c8e2af63690efa4

libm/Android.mk

@@ -239,6 +239,7 @@ libm_common_cflags := \
     -Wno-sign-compare \
     -Wno-uninitialized \
     -Wno-unknown-pragmas \
+    -fvisibility=hidden \
 
 libm_common_includes := $(LOCAL_PATH)/upstream-freebsd/lib/msun/src/
 

libm/include/fenv.h

@@ -34,6 +34,7 @@
 #include <machine/fenv.h>
 
 __BEGIN_DECLS
+#pragma GCC visibility push(default)
 
 int feclearexcept(int);
 int fegetexceptflag(fexcept_t *, int);
@@ -64,6 +65,7 @@ int fegetexcept(void);
 extern const fenv_t __fe_dfl_env;
 #define FE_DFL_ENV  (&__fe_dfl_env)
 
+#pragma GCC visibility pop
 __END_DECLS
 
 #endif  /* ! _FENV_H_ */

libm/include/math.h

@@ -20,6 +20,9 @@
 #include <sys/cdefs.h>
 #include <limits.h>
 
+__BEGIN_DECLS
+#pragma GCC visibility push(default)
+
 /*
  * ANSI/POSIX
  */
@@ -165,7 +168,7 @@ extern int signgam;
  * effect of raising floating-point exceptions, so they are not declared
  * as __pure2.  In C99, FENV_ACCESS affects the purity of these functions.
  */
-__BEGIN_DECLS
+
 /*
  * ANSI/POSIX
  */
@@ -282,6 +285,7 @@ double	trunc(double);
 double	drem(double, double);
 int	finite(double) __pure2;
 int	isnanf(float) __pure2;
+long double significandl(long double);
 
 /*
  * Reentrant version of gamma & lgamma; passes signgam back by reference
@@ -464,6 +468,7 @@ void sincosf(float, float*, float*);
 void sincosl(long double, long double*, long double*);
 #endif /* _GNU_SOURCE */
 
+#pragma GCC visibility pop
 __END_DECLS
 
 #endif /* !_MATH_H_ */

tests/math_test.cpp

@@ -1067,8 +1067,6 @@ TEST(math, significandf) {
   ASSERT_FLOAT_EQ(1.5375f, significandf(12.3f));
 }
 
-extern "C" long double significandl(long double); // BSD's <math.h> doesn't declare this.
-
 TEST(math, significandl) {
   ASSERT_DOUBLE_EQ(0.0L, significandl(0.0L));
   ASSERT_DOUBLE_EQ(1.2L, significandl(1.2L));