debug: don't set end_location at function exit

[asterite]

The codegen was setting the end location of a method for the last return LLVM instruction.

So for example for this code:

def foo
  bar
end

def bar
  a = [1]
  a[2]
end

foo

we would get:

Index out of bounds (IndexError)
0x10d77753e: at at /usr/local/Cellar/crystal-lang/0.23.1/src/indexable.cr 0:17
0x10d7774d9: [] at /usr/local/Cellar/crystal-lang/0.23.1/src/indexable.cr 74:5
0x10d75da51: bar at /Users/asterite/Projects/crystal/foo.cr 8:3
0x10d75d9d9: foo at /Users/asterite/Projects/crystal/foo.cr 3:3
0x10d74d807: __crystal_main at /Users/asterite/Projects/crystal/foo.cr 10:1
0x10d75d8b8: main at /usr/local/Cellar/crystal-lang/0.23.1/src/main.cr 12:15

foo.cr at line 3 is the end, but it should be foo.cr at line 2, bar.

The same goes for indexable.cr at line 74, it points to the end where it should point to the last expression (one line above it).

The solution is to leave the debug info for the last return LLVM instruction as the location of the previously executed expression.

The indexable.cr line 0 is still a mistery, but it must be an unrelated issue.

[RX14]

Perhaps we could use the crystal compiler programatically to ensure we don't have to handle multiple compiler versions, just master.

[asterite]

It's a good idea. I'll change it later.

[asterite]

Actually, I'd prefer now to do that just now. That means the spec will depend on the compiler, and that will slow down std_spec a lot.

[RX14]

This looks like a great fix, but regarding specs I think we should do something like #4718 sooner or later. I think sticking all debuginfo specs inside "callstack" is a bad idea.

[asterite]

@RX14 I agree. I just fixed the spec because it was failing. It's just coincidence that there's a spec for this (I'm sure it's testing the callstack, not the debug info location)

[ysbaddaden]

Yes, the spec is testing that the DWARF information (function name, file:line:colum) is correctly parsed and printed, so we don't have regressions, and we get a failure when porting to an unsupported system (can't parse executable, failed to find/parse DWARF).