Negative line number in stacktrace exception

[Kartatz]

The following code snippet generates a stacktrace exception pointing to a invalid line number (-1):

with object() as obj:
	break

Example:

$ echo 'with object() as obj:\n\tbreak' > main.py
$ python main.py
  File "/home/kartz/main.py", line -1
SyntaxError: 'break' outside loop

This is reproducible with Python 3.10, 3.11 and latest master. I could not reproduce this on Python versions older than <3.10.

Linked PRs

• gh-101400: Fix incorrect lineno in exception message on continue/break which are not in a loop #101413
• [3.11] gh-101400: Fix incorrect lineno in exception message on contin… #101447
• [3.10] gh-101400: Fix incorrect lineno in exception message on contin… #101448

[corona10]

@iritkatriel

The bug is triggered from this line:

cpython/Python/compile.c

Line 2069 in 666c084

*ploc = NO_LOCATION;

with object() as obj:
    continue

#   File "/Users/user/oss/cpython/gh-101400.py", line -1
# SyntaxError: 'continue' not properly in loop

Same issue with continue

[corona10]

This kind of fix will solve the issue, but I am not sure this is the right approach.

diff --git a/Python/compile.c b/Python/compile.c
index c31f08c0a1..18cf1382f5 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -3248,9 +3248,10 @@ compiler_break(struct compiler *c, location loc)
     struct fblockinfo *loop = NULL;
+    location origin_loc = loc;
     /* Emit instruction with line number */
     ADDOP(c, loc, NOP);
     RETURN_IF_ERROR(compiler_unwind_fblock_stack(c, &loc, 0, &loop));
     if (loop == NULL) {
-        return compiler_error(c, loc, "'break' outside loop");
+        return compiler_error(c, origin_loc, "'break' outside loop");
     }
     RETURN_IF_ERROR(compiler_unwind_fblock(c, &loc, loop, 0));
     ADDOP_JUMP(c, loc, JUMP, loop->fb_exit);
@@ -3261,11 +3262,12 @@ static int
 compiler_continue(struct compiler *c, location loc)
 {
     struct fblockinfo *loop = NULL;
+    location origin_loc = loc;
     /* Emit instruction with line number */
     ADDOP(c, loc, NOP);
     RETURN_IF_ERROR(compiler_unwind_fblock_stack(c, &loc, 0, &loop));
     if (loop == NULL) {
-        return compiler_error(c, loc, "'continue' not properly in loop");
+        return compiler_error(c, origin_loc, "'continue' not properly in loop");
     }
     ADDOP_JUMP(c, loc, JUMP, loop->fb_block);
     return SUCCESS;

[iritkatriel]

@corona10 your fix looks right. Do you want to make a PR? We would need a couple of tests for this.

[corona10]

I will submit the patch ;)

[corona10]

Now we can close the issue. Please let me know if we have to reopen the issue.

Thanks for the report @Kartatz
And thanks for the kind reviews!! @iritkatriel :)