-------------
import std;
void fun(void delegate() dg) {
dg();
}
void main() {
int x = 123;
string y = "abc";
writeln(y);
fun({
x++;
y ~= "d";
});
}
-------------
Compile with `dmd -g prog.d`. In gdb, set a breakpoint for prog.main:
-------------
(gdb) break prog.main
Breakpoint 1 at 0xe1c34: file prog.d, line 10.
(gdb) run
Starting program: /tmp/prog
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
abc
Breakpoint 1, prog.main().__lambda3() (__capture=0x7ffff7cad000) at prog.d:10
10 x++;
(gdb)
-------------
This is wrong; the breakpoint for prog.main should break at the `writeln` line, or one of the variable initializers. But instead, it breaks inside the delegate body. A backtrace shows that `fun` has already been called.
Expected behaviour: breaking at a function should break at the beginning of the function, not in the middle, and certainly not inside the body of a delegate!
Comment #1 by lucien.perregaux — 2021-04-18T20:41:26Z
There is two bugs:
1. `break prog.main` should say `Function "prog.main" not defined.` (because of https://issues.dlang.org/show_bug.cgi?id=21160), but it breaks somewhere else (end of f() in this case)
---
void main()
{
int x = 123;
void f()
{
x++;
}
}
---
Removing `f()` produce `Function "prog.main" not defined.` ("normal" behaviour).
2. Using `writeln` writes wrong data in the dwarf debug infos.
---
import std.stdio;
void main()
{
writeln("x");
}
---
`llvm-dwarfdump prog`:
--
error: unexpected end of data at offset 0x804 while reading [0x15, 0x4d1d)
error: unexpected end of data at offset 0x804 while reading [0x15, 0x4d1d)
0x00000789: DW_TAG_subprogram
DW_AT_sibling (0x00000852)
DW_AT_name ("std.exception.bailOut!(std.exception.ErrnoException).bailOut")
DW_AT_MIPS_linkage_name ("_D3std9exception__T7bailOutHTCQBcQBb14ErrnoExceptionZQBiFNfAyamMAxaZv")
DW_AT_decl_file ("phobos/std/exception.d")
DW_AT_decl_line (512)
DW_AT_low_pc (0x000000000004db00)
DW_AT_high_pc (0x000000000004db7c)
DW_AT_frame_base (0x00000214:
[0x000000000004db00, 0x000000000004db01): DW_OP_breg7 RSP+8
[0x000000000004db01, 0x000000000004db03): DW_OP_breg7 RSP+16
[0x000000000004db03, 0x000000000004db7c): DW_OP_breg6 RBP+16)
0x00000828: DW_TAG_formal_parameter
DW_AT_name ("msg")
DW_AT_type (0x000004f0 "_Array_char")
DW_AT_artificial (0x00)
DW_AT_location (DW_OP_fbreg -64)
---
Something in bailOut is not correctly emitted / not supported.
Comment #2 by robert.schadek — 2024-12-13T19:15:31Z