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Add -C link-dead-code option r=alexcrichton

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Turning gc-sections off improves code coverage based for tools which
use DWARF debugging information (like kcov). Otherwise dead code is
stripped and kcov returns a coverage percentage that doesn't reflect
reality.
This commit is contained in:
Johan Lorenzo 2016-02-02 17:56:59 +00:00
parent b9732ed147
commit 274f27a476
3 changed files with 12 additions and 1 deletions
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2
src/librustc/session/config.rs
View file

@ -507,6 +507,8 @@ options! {CodegenOptions, CodegenSetter, basic_codegen_options,
"system linker to link outputs with"),
link_args: Option<Vec<String>> = (None, parse_opt_list,
"extra arguments to pass to the linker (space separated)"),
link_dead_code: bool = (false, parse_bool,
"let the linker strip dead coded (turning it on can be used for code coverage)"),
lto: bool = (false, parse_bool,
"perform LLVM link-time optimizations"),
target_cpu: Option<String> = (None, parse_opt_string,

4
src/librustc_trans/back/link.rs
View file

@ -976,7 +976,9 @@ fn link_args(cmd: &mut Linker,
// Try to strip as much out of the generated object by removing unused
// sections if possible. See more comments in linker.rs
cmd.gc_sections(dylib);
if !sess.opts.cg.link_dead_code {
cmd.gc_sections(dylib);
}
let used_link_args = sess.cstore.used_link_args();

7
src/test/run-make/codegen-options-parsing/Makefile
View file

@ -22,3 +22,10 @@ all:
$(RUSTC) -C lto=foo dummy.rs 2>&1 | \
grep 'codegen option `lto` takes no value'
$(RUSTC) -C lto dummy.rs
# Should not link dead code...
$(RUSTC) -Z print-link-args dummy.rs 2>&1 | \
grep -e '--gc-sections\|-dead_strip\|/OPT:REF,ICF'
# ... unless you specifically ask to keep it
$(RUSTC) -Z print-link-args -C link-dead-code dummy.rs 2>&1 | \
(! grep -e '--gc-sections\|-dead_strip\|/OPT:REF,ICF')