Mercurial > cpython-lru_cache-weakref

diff Python/ceval.c @ 54297:dddf424bd669 legacy-trunk

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Issue #6042: lnotab-based tracing is very complicated and isn't documented very well. There were at least 3 comment blocks purporting to document co_lnotab, and none did a very good job. This patch unifies them into Objects/lnotab_notes.txt which tries to completely capture the current state of affairs. I also discovered that we've attached 2 layers of patches to the basic tracing scheme. The first layer avoids jumping to instructions that don't start a line, to avoid problems in if statements and while loops. The second layer discovered that jumps backward do need to trace at instructions that don't start a line, so it added extra lnotab entries for 'while' and 'for' loops, and added a special case for backward jumps within the same line. I replaced these patches by just treating forward and backward jumps differently.
author Jeffrey Yasskin <jyasskin@gmail.com>
date Sat, 23 May 2009 23:23:01 +0000
parents 9ef683d41c9b
children 145376df3ad7
line wrap: on
line diff
--- a/Python/ceval.c	Sat May 23 21:48:06 2009 +0000
+++ b/Python/ceval.c	Sat May 23 23:23:01 2009 +0000
@@ -3591,33 +3591,30 @@
 	return result;
 }
 
+/* See Objects/lnotab_notes.txt for a description of how tracing works. */
 static int
 maybe_call_line_trace(Py_tracefunc func, PyObject *obj,
 		      PyFrameObject *frame, int *instr_lb, int *instr_ub,
 		      int *instr_prev)
 {
 	int result = 0;
+	int line = frame->f_lineno;
 
         /* If the last instruction executed isn't in the current
-           instruction window, reset the window.  If the last
-           instruction happens to fall at the start of a line or if it
-           represents a jump backwards, call the trace function.
+           instruction window, reset the window.
         */
-	if ((frame->f_lasti < *instr_lb || frame->f_lasti >= *instr_ub)) {
-		int line;
+	if (frame->f_lasti < *instr_lb || frame->f_lasti >= *instr_ub) {
 		PyAddrPair bounds;
-
-		line = PyCode_CheckLineNumber(frame->f_code, frame->f_lasti,
-					      &bounds);
-		if (line >= 0) {
-			frame->f_lineno = line;
-			result = call_trace(func, obj, frame,
-					    PyTrace_LINE, Py_None);
-		}
+		line = _PyCode_CheckLineNumber(frame->f_code, frame->f_lasti,
+					       &bounds);
 		*instr_lb = bounds.ap_lower;
 		*instr_ub = bounds.ap_upper;
 	}
-	else if (frame->f_lasti <= *instr_prev) {
+	/* If the last instruction falls at the start of a line or if
+           it represents a jump backwards, update the frame's line
+           number and call the trace function. */
+	if (frame->f_lasti == *instr_lb || frame->f_lasti < *instr_prev) {
+		frame->f_lineno = line;
 		result = call_trace(func, obj, frame, PyTrace_LINE, Py_None);
 	}
 	*instr_prev = frame->f_lasti;