September 17

I've just reached something strange when debugging code, here's a repro:

  1. create bad_debug_lines.d with the following content
module bad_debug_lines;

extern(C) int rand();

int call() {
    return 1 + rand() % 8; // defeat opts...
}

void main() {
    if (call() &&
        call() &&
        call() &&
        call())
    {}
}
  1. in a console
[xxxx@pc temp]$ gdb ./bad_debug_lines
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For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from ./bad_debug_lines...
(gdb) b bad_debug_lines.d:10
Breakpoint 1 at 0x402758: file bad_debug_lines.d, line 10.
(gdb) b bad_debug_lines.d:11
Breakpoint 2 at 0x4027ba: file bad_debug_lines.d, line 15.
(gdb) b bad_debug_lines.d:12
Note: breakpoint 2 also set at pc 0x4027ba.
Breakpoint 3 at 0x4027ba: file bad_debug_lines.d, line 15.
(gdb) b bad_debug_lines.d:13
Note: breakpoints 2 and 3 also set at pc 0x4027ba.
Breakpoint 4 at 0x4027ba: file bad_debug_lines.d, line 15.
(gdb) run
Starting program: /home/basile/Bureau/temp/bad_debug_lines
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Breakpoint 1, D main () at bad_debug_lines.d:10
10          if (call() &&
Missing separate debuginfos, use: dnf debuginfo-install glibc-2.32-10.fc33.x86_64 libgcc-10.3.1-1.fc33.x86_64
(gdb) c
Continuing.

Breakpoint 2, D main () at bad_debug_lines.d:15
15      }
(gdb) q
A debugging session is active.

        Inferior 1 [process 15789] will be killed.

Quit anyway? (y or n) y

so it's not possible to debug conditions in && (same for OrOrExp btw), even when the operands stand on their own line.

At least two breakpoints should work. That seems to be the case but the
second indicates line 15.

The problem is somewhat confirmed by the IR view:
https://godbolt.org/z/bsfaPvPbE, as you can see the coloured block for the ifcondition is only 1 line long.

September 17

On Friday, 17 September 2021 at 13:42:48 UTC, Basile B wrote:

>

I've just reached something strange when debugging code, here's a repro:

  1. create bad_debug_lines.d with the following content
module bad_debug_lines;

extern(C) int rand();

int call() {
    return 1 + rand() % 8; // defeat opts...
}

void main() {
    if (call() &&
        call() &&
        call() &&
        call())
    {}
}

[...]

>

The problem is somewhat confirmed by the IR view:
https://godbolt.org/z/bsfaPvPbE, as you can see the coloured block for the ifcondition is only 1 line long.

Yeah I've known about this issue for a long time. Haven't found the time to fix it. Your post does add a little motivation for fixing it :)

-Johan