[Bug c/89410] [7/8/9 Regression] ICE in calculate_line_spans, at diagnostic-show-locus.c:1237 after #line

[jg at jguk dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89410

--- Comment #12 from Jonny Grant <jg at jguk dot org> ---
Just to add

C spec says UB.

http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf

"The #line preprocessing directive that results after expansion does not match
one of
the two well-defined forms, or its digit sequence specifies zero or a number
greater
than 2147483647 (6.10.4)."

As I understand it, it is #line <the next line will be numbered>
So if it is #line 1, the following line (actual line 2) will be counted as line
1.

#line 0, means that the actual 2nd line in a file is treated as 0.