gdb has the wrong source location with many macros

[alexcrichton]

#![feature(macro_rules)]                             

macro_rules! call2( ($e:expr) => ($e()) )            
macro_rules! call( ($e:expr) => (handle(call2!($e))) )

fn bar() {                                           
    unsafe {                                         
        *(0 as *mut uint) = 0;                       
    }                                                
}                                                    

fn foo() {                                           
    call!(bar);                                      
}                                                    

fn handle(_:()) {}                                   

fn main() {                                          
    foo();                                           
}                                                    

$ rustc foo.rs -g
$ gdb ./foo
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Reading symbols from ./main...done.
(gdb) r
Starting program: /home/alex/code/foobar/main 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Program received signal SIGSEGV, Segmentation fault.
main::bar () at src/main.rs:8
8               *(0 as *mut uint) = 0;
(gdb) bt
#0  main::bar () at src/main.rs:8
#1  0x000055555555f32e in main::foo () at src/main.rs:4
#2  0x000055555555f39e in main::main () at src/main.rs:19
#3  0x00005555555950eb in start::closure.8511 ()
#4  0x00005555555acbfc in rust_try_inner ()
#5  0x00005555555acbe6 in rust_try ()
#6  0x00005555555aa533 in unwind::try::hd12740a912640cc1imd ()
#7  0x00005555555aa3fc in task::Task::run::ha62f1c0aea75bedcWBc ()
#8  0x0000555555594f27 in start::h239c3a425c3165f7ehe ()
#9  0x0000555555594d68 in lang_start::hb36b8d7630529d77xge ()
#10 0x000055555555f3ef in main ()

The line number for the stack frame of main::foo says it's on line 4, when it should actually be lower than that. I have noticed, however, that if there's only one macro (e.g. call2 goes away) the source location is correct. This may be a bug in debuginfo, but it may also be a bug in macros in general (source locations aren't always quite correct I think).

cc @michaelwoerister

[michaelwoerister]

Might be related to #23480.

[aij]

This bug makes debugging errors returned through try! really annoying.

[huonw]

cc #9232, #17234

[jethrogb]

Will this magically get fixed when #23480 is fixed?

[jseyfried]

Yeah, this looks like a consequence of #23480 / #39450.
This should be fixed by span reform along the road to declarative macros 2.0.