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MIR codegen attributes cleanups to beginning of the lexical block. #37032

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vadimcn opened this issue Oct 7, 2016 · 2 comments
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MIR codegen attributes cleanups to beginning of the lexical block. #37032

vadimcn opened this issue Oct 7, 2016 · 2 comments
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A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.)

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@vadimcn
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vadimcn commented Oct 7, 2016

Compile this code with debug info (-g):

1: fn main() {
2:     zzz();
3:     let s = String::from("sss");
4:     zzz();
5: }
6: 
7: fn zzz() {}

Set a breakpoint on line 2 and start line-stepping. The line position order will be something like this: 2, 3, 4, 3 (cleanup for s), 1 (epilogue for main).
I think everyone will agree that it would make much more sense to attribute the last two to line 5.

The fix will probably need to be done in rustc_trans::mir::MirContext::trans_block.
Also, this probably means that mir::SourceInfo should carry a Pos, not a Span (we only ever use span.lo anyways).
@vadimcn vadimcn added the A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) label Oct 7, 2016
@vadimcn
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vadimcn commented Oct 7, 2016

cc @michaelwoerister, @eddyb. Amirite about trans_block()?

@michaelwoerister
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I haven't looked at this in detail but I agree that it would make sense to associate cleanup with the end of the scope. Old-trans did it this way.

@vadimcn vadimcn mentioned this issue Oct 20, 2016
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Manishearth added a commit to Manishearth/rust that referenced this issue Oct 22, 2016
@Manishearth
Rollup merge of rust-lang#37310 - vadimcn:drop-spans, r=michaelwoerister
14e7c6d 
Fix line stepping in debugger.

Attribute drop code to block's closing brace, instead of the line where the allocation was done.
Attribute function epilogues to function body's closing brace, rather than the function header.

Fixes rust-lang#37032

r? @michaelwoerister
bors added a commit that referenced this issue Oct 22, 2016
@bors
Auto merge of #37310 - vadimcn:drop-spans, r=michaelwoerister
0eb4d46 
Fix line stepping in debugger.

Attribute drop code to block's closing brace, instead of the line where the allocation was done.
Attribute function epilogues to function body's closing brace, rather than the function header.

Fixes #37032

r? @michaelwoerister
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A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.)
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