https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109591
Bug ID: 109591
Summary: Multiple -fdebug-prefix-map= prefixes match, which one
wins?
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: i at maskray dot me
Target Milestone: ---
mkdir -p a/b/c
echo 'int main(){}' > a/b/c/d.c
~/Dev/gcc/out/release/gcc/xgcc -B ~/Dev/gcc/out/release/gcc -g -c
-fdebug-prefix-map=a/b/c=z -fdebug-prefix-map=a/b=y -fdebug-prefix-map=a=x
a/b/c/d.c
objdump -Wi d.o | grep 'd\.c' # <12> DW_AT_name : (indirect line
string, offset: 0): x/b/c/d.c
~/Dev/gcc/out/release/gcc/xgcc -B ~/Dev/gcc/out/release/gcc -g -c
-fdebug-prefix-map=a=x -fdebug-prefix-map=a/b=y -fdebug-prefix-map=a/b/c=z
a/b/c/d.c
objdump -Wi d.o | grep 'd\.c' # <12> DW_AT_name : (indirect line
string, offset: 0): z/d.c
return
When multiple -fdebug-prefix-map= options are applicable, it seems that the
last wins.
In Clang, after https://reviews.llvm.org/D49466 (landed in Nov 2019), the
longest prefix wins.
clang -g -c -fdebug-prefix-map=a=x -fdebug-prefix-map=a/b=y
-fdebug-prefix-map=a/b/c=z a/b/c/d.c # z/d.c
clang -g -c -fdebug-prefix-map=a=x -fdebug-prefix-map=a/b=y
-fdebug-prefix-map=a/b/c=z a/b/c/d.c # z/d.c
This issue is motivated by https://reviews.llvm.org/D148757
---
Related, there is a strange use case where the old prefix is empty. The new
prefix may or may not end with a slash: '-fdebug-prefix-map==w' and
'-fdebug-prefix-map==w/'.
'-fdebug-prefix-map==w' changes the file name to wa/b/c/d.c . I am unsure
whether it should be w/a/b/c/d.c instead. Clang has the same problem.
