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Add auto deduce source map setting
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Authored by yinghuitan on Sep 14 2022, 5:24 PM.

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Summary
This patch adds a new "target.auto-deduce-source-map" setting.

If enabled, this setting may auto deduce a source map entry based on requested
breakpoint path and the original path stored in debug info for resolved
breakpoint.

As an example, if debug info contains "./a/b/c/main.cpp", user sets a source
breakpoint at "/root/repo/x/y/z/a/b/c/main.cpp". The breakpoint will resolve
correctly now with Greg's patch https://reviews.llvm.org/D130401. However, the
resolved breakpoint will use "./a/b/c/main.cpp" to locate source file during
stop event which would fail most of the time.

With the new "target.auto-deduce-source-map" setting enabled, a auto deduced
source map entry "." => "/root/repo/x/y/z" will be added. This new mapping will
help lldb to map resolved breakpoint path "./a/b/c/main.cpp" back to
"/root/repo/x/y/z/a/b/c/main.cpp" and locate it on disk.

If an existing source map entry is used the patch also concatenates the auto
deduced entry with any stripped reverse mapping prefix (see example below).

As a second example, debug info contains "./a/b/c/main.cpp" and user sets
breakpoint at "/root/repo/x/y/z/a/b/c/main.cpp". Let's say there is an existing
source map entry "." => "/root/repo"; this mapping would strip the prefix out of
"/root/repo/x/y/z/a/b/c/main.cpp" and use "x/y/z/a/b/c/main.cpp" to resolve
breakpoint. "target.auto-deduce-source-map" setting would auto deduce a new
potential mapping of "." => "x/y/z", then it detects that there is a stripped
prefix from reverse mapping and concatenates it as the new mapping:
 "." => "/root/repo/x/y/z" which would correct map "./a/b/c/main.cpp" path to
new path in disk.

This patches depends on https://reviews.llvm.org/D130401 to use new added
SBTarget::GetSourceMap() API for testing.

Differential Revision: https://reviews.llvm.org/D133042

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yinghuitan created this revision.Sep 14 2022, 5:24 PM
Herald added a project: Restricted Project. · View Herald TranscriptSep 14 2022, 5:24 PM
yinghuitan requested review of this revision.Sep 14 2022, 5:24 PM
Herald added a project: Restricted Project. · View Herald TranscriptSep 14 2022, 5:24 PM
yinghuitan abandoned this revision.Sep 14 2022, 5:27 PM

We also inject a source-map behind the scenes when a dSYM has path mapping keys as described in:

https://lldb.llvm.org/use/symbols.html

It would be good to make sure that the auto-detect source maps and that feature get along nicely both when the dSYM source map points to the right directory, and when it to is stale and points to some path that's not available.