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Auto merge of #121297 - michaelwoerister:set-pdb-alt-path, r=wesleywiser
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link.exe: Don't embed full path to PDB file in binary.

This PR makes `rustc` unconditionally pass `/PDBALTPATH:%_PDB%` to MSVC-style linkers, causing the linker to only embed the filename of the PDB in the binary instead of the full path. This will help implement the [trim-paths RFC](#111540) for `*-msvc` targets.

Passing `/PDBALTPATH:%_PDB%` to the linker is already done by many projects that need reproducible builds and [debugger's should still be able to find the PDB](https://learn.microsoft.com/cpp/build/reference/pdbpath) if it is in the same directory as the binary.

r? `@ghost`

Fixes #87825
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bors committed Mar 15, 2024
2 parents accc516 + 0a094ba commit c5b5713
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9 changes: 9 additions & 0 deletions compiler/rustc_codegen_ssa/src/back/linker.rs
Original file line number Diff line number Diff line change
Expand Up @@ -929,6 +929,15 @@ impl<'a> Linker for MsvcLinker<'a> {
// from the CodeView line tables in the object files.
self.cmd.arg("/DEBUG");

// Default to emitting only the file name of the PDB file into
// the binary instead of the full path. Emitting the full path
// may leak private information (such as user names).
// See https://github.com/rust-lang/rust/issues/87825.
//
// This default behavior can be overridden by explicitly passing
// `-Clink-arg=/PDBALTPATH:...` to rustc.
self.cmd.arg("/PDBALTPATH:%_PDB%");

// This will cause the Microsoft linker to embed .natvis info into the PDB file
let natvis_dir_path = self.sess.sysroot.join("lib\\rustlib\\etc");
if let Ok(natvis_dir) = fs::read_dir(&natvis_dir_path) {
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20 changes: 20 additions & 0 deletions tests/run-make/pdb-alt-path/Makefile
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@@ -0,0 +1,20 @@
include ../tools.mk

# only-windows-msvc

all:
# Test that we don't have the full path to the PDB file in the binary
$(RUSTC) main.rs -g --crate-name my_crate_name --crate-type bin -Cforce-frame-pointers
$(CGREP) "my_crate_name.pdb" < $(TMPDIR)/my_crate_name.exe
$(CGREP) -v "\\my_crate_name.pdb" < $(TMPDIR)/my_crate_name.exe

# Test that backtraces still can find debuginfo by checking that they contain symbol names and
# source locations.
$(TMPDIR)/my_crate_name.exe &> $(TMPDIR)/backtrace.txt
$(CGREP) "my_crate_name::fn_in_backtrace" < $(TMPDIR)/backtrace.txt
$(CGREP) "main.rs:15" < $(TMPDIR)/backtrace.txt

# Test that explicitly passed `-Clink-arg=/PDBALTPATH:...` is respected
$(RUSTC) main.rs -g --crate-name my_crate_name --crate-type bin -Clink-arg=/PDBALTPATH:abcdefg.pdb -Cforce-frame-pointers
$(CGREP) "abcdefg.pdb" < $(TMPDIR)/my_crate_name.exe
$(CGREP) -v "my_crate_name.pdb" < $(TMPDIR)/my_crate_name.exe
24 changes: 24 additions & 0 deletions tests/run-make/pdb-alt-path/main.rs
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@@ -0,0 +1,24 @@
// The various #[inline(never)] annotations and std::hint::black_box calls are
// an attempt to make unwinding as non-flaky as possible on i686-pc-windows-msvc.

#[inline(never)]
fn generate_backtrace(x: &u32) {
std::hint::black_box(x);
let bt = std::backtrace::Backtrace::force_capture();
println!("{}", bt);
std::hint::black_box(x);
}

#[inline(never)]
fn fn_in_backtrace(x: &u32) {
std::hint::black_box(x);
generate_backtrace(x);
std::hint::black_box(x);
}

fn main() {
let x = &41;
std::hint::black_box(x);
fn_in_backtrace(x);
std::hint::black_box(x);
}

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