Merge pull request apple#81 from stephentyrone/lgamma-shims-linux

Add inline decls of lgamma_r and friends on Linux, too.

Sources/NumericsShims/include/NumericsShims.h

@@ -11,8 +11,22 @@
 
 #define HEADER_SHIM static inline __attribute__((__always_inline__))
 
-// MARK: - math functions for float
+// This header uses most of the libm functions, but we don't want to end up
+// exporting the libm declarations to modules that include NumericsShims, so
+// we don't want to actually #include <math.h>.
+//
+// For most of the functions, we can get around this by using __builtin_func
+// instead of func, since the compiler knows about these operations, but for
+// the non-standard extensions, we need to include our own declarations. This
+// is a little bit risky, in that we might end up missing an attribute that
+// gets added and effects calling conventions, etc, but that's expected to be
+// exceedingly rare.
+//
+// Still, we'll eventually want to find a better solution to this problem,
+// especially if people start using this package on systems that are not
+// Darwin or Ubuntu.
 
+// MARK: - math functions for float
 HEADER_SHIM float libm_cosf(float x) {
   return __builtin_cosf(x);
 }
@@ -131,9 +145,7 @@ HEADER_SHIM float libm_log10f(float x) {
 
 #if !defined _WIN32
 HEADER_SHIM float libm_lgammaf(float x, int *signp) {
-#if __APPLE__
   extern float lgammaf_r(float, int *);
-#endif
   return lgammaf_r(x, signp);
 }
 #endif
@@ -253,9 +265,7 @@ HEADER_SHIM double libm_log10(double x) {
 
 #if !defined _WIN32
 HEADER_SHIM double libm_lgamma(double x, int *signp) {
-#if __APPLE__
   extern double lgamma_r(double, int *);
-#endif
   return lgamma_r(x, signp);
 }
 #endif