style: make these macros more bullet-proof

Author: nedbat

Diff for: coverage/ctracer/tracer.c

@@ -523,7 +523,7 @@ CTracer_handle_call(CTracer *self, PyFrameObject *frame)
      * re-entering a generator also.  f_lasti is -1 for a true call, and a
      * real byte offset for a generator re-entry.
      */
-    if (frame->f_lasti < 0) {
+    if (MyFrame_lasti(frame) < 0) {
         self->pcur_entry->last_line = -MyFrame_GetCode(frame)->co_firstlineno;
     }
     else {

Diff for: coverage/ctracer/util.h

@@ -15,17 +15,17 @@
 // The f_lasti field changed meaning in 3.10.0a7. It had been bytes, but
 // now is instructions, so we need to adjust it to use it as a byte index.
 #if PY_VERSION_HEX >= 0x030A00A7
-#define MyFrame_lasti(f)    (f->f_lasti * 2)
+#define MyFrame_lasti(f)    ((f)->f_lasti * 2)
 #else
-#define MyFrame_lasti(f)    f->f_lasti
-#endif // 3.10.0a7
+#define MyFrame_lasti(f)    ((f)->f_lasti)
+#endif
 
 // Access f_code should be done through a helper starting in 3.9.
 #if PY_VERSION_HEX >= 0x03090000
 #define MyFrame_GetCode(f)      (PyFrame_GetCode(f))
 #else
 #define MyFrame_GetCode(f)      ((f)->f_code)
-#endif // 3.11
+#endif
 
 /* The values returned to indicate ok or error. */
 #define RET_OK      0