[Bug #19635] Preserve `errno`

The following functions are turned into macros and no longer can be
used as expressions in core.
- rb_sys_fail
- rb_sys_fail_str
- rb_sys_fail_path

error.c

@@ -3312,12 +3312,14 @@ rb_syserr_fail_str(int e, VALUE mesg)
     rb_exc_raise(rb_syserr_new_str(e, mesg));
 }
 
+#undef rb_sys_fail
 void
 rb_sys_fail(const char *mesg)
 {
     rb_exc_raise(make_errno_exc(mesg));
 }
 
+#undef rb_sys_fail_str
 void
 rb_sys_fail_str(VALUE mesg)
 {

internal/error.h

@@ -29,15 +29,31 @@
 #define rb_raise_static(e, m) \
     rb_raise_cstr_i((e), rb_str_new_static((m), rb_strlen_lit(m)))
 #ifdef RUBY_FUNCTION_NAME_STRING
-# define rb_sys_fail_path(path) rb_sys_fail_path_in(RUBY_FUNCTION_NAME_STRING, path)
 # define rb_syserr_fail_path(err, path) rb_syserr_fail_path_in(RUBY_FUNCTION_NAME_STRING, (err), (path))
 # define rb_syserr_new_path(err, path) rb_syserr_new_path_in(RUBY_FUNCTION_NAME_STRING, (err), (path))
 #else
-# define rb_sys_fail_path(path) rb_sys_fail_str(path)
 # define rb_syserr_fail_path(err, path) rb_syserr_fail_str((err), (path))
 # define rb_syserr_new_path(err, path) rb_syserr_new_str((err), (path))
 #endif
 
+#define rb_sys_fail(mesg) \
+do { \
+    int errno_to_fail = errno; \
+    rb_syserr_fail(errno_to_fail, (mesg)); \
+} while (0)
+
+#define rb_sys_fail_str(mesg) \
+do { \
+    int errno_to_fail = errno; \
+    rb_syserr_fail_str(errno_to_fail, (mesg)); \
+} while (0)
+
+#define rb_sys_fail_path(path) \
+do { \
+    int errno_to_fail = errno; \
+    rb_syserr_fail_path(errno_to_fail, (path)); \
+} while (0)
+
 /* error.c */
 extern long rb_backtrace_length_limit;
 extern VALUE rb_eEAGAIN;