Re: [PATCH RFC 03/11] rust: Use absolute paths to build Rust objects

Asahi Lina <lina@xxxxxxxxxxxxx> · Sun, 16 Jul 2023 16:53:57 +0900

On 15/07/2023 23.35, Gary Guo wrote:
On Fri, 14 Jul 2023 18:13:55 +0900
Asahi Lina <lina@xxxxxxxxxxxxx> wrote:

We want to use caller_location to uniquely identify callsites, to
automatically create lockdep classes without macros. The location
filename in local code uses the relative path passed to the compiler,
but if that code is generic and instantiated from another crate, the
path becomes absolute.

To make this work and keep the paths consistent, always pass an absolute
path to the compiler. Then the Location path is always identical
regardless of how the code is being compiled.

I wonder if this can have some reproducible build implications. We
probably also need to use remap-path-prefix?

We already end up with absolute paths in objects anyway, just not 
consistently. If it were consistently relative paths that would be fine 
too, but it looks like Rust likes to internally absolute-ize some paths, 
that's why I wrote this patch to make it always like that.

TIL about remap-path-prefix, that looks very useful! I'll give it a try.



Signed-off-by: Asahi Lina <lina@xxxxxxxxxxxxx>
---
  rust/Makefile          | 2 +-
  scripts/Makefile.build | 8 ++++----
  2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/rust/Makefile b/rust/Makefile
index 7c9d9f11aec5..552f023099c8 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -369,7 +369,7 @@ quiet_cmd_rustc_library = $(if $(skip_clippy),RUSTC,$(RUSTC_OR_CLIPPY_QUIET)) L
  		--emit=dep-info=$(depfile) --emit=obj=$@ \
  		--emit=metadata=$(dir $@)$(patsubst %.o,lib%.rmeta,$(notdir $@)) \
  		--crate-type rlib -L$(objtree)/$(obj) \
-		--crate-name $(patsubst %.o,%,$(notdir $@)) $< \
+		--crate-name $(patsubst %.o,%,$(notdir $@)) $(abspath $<) \
  	$(if $(rustc_objcopy),;$(OBJCOPY) $(rustc_objcopy) $@)
  
  rust-analyzer:
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 6413342a03f4..c925b90ebd80 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -283,27 +283,27 @@ rust_common_cmd = \
  # would not match each other.
  
  quiet_cmd_rustc_o_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
-      cmd_rustc_o_rs = $(rust_common_cmd) --emit=obj=$@ $<
+      cmd_rustc_o_rs = $(rust_common_cmd) --emit=obj=$@ $(abspath $<)
  
  $(obj)/%.o: $(src)/%.rs FORCE
  	$(call if_changed_dep,rustc_o_rs)
  
  quiet_cmd_rustc_rsi_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
        cmd_rustc_rsi_rs = \
-	$(rust_common_cmd) -Zunpretty=expanded $< >$@; \
+	$(rust_common_cmd) -Zunpretty=expanded $(abspath $<) >$@; \
  	command -v $(RUSTFMT) >/dev/null && $(RUSTFMT) $@
  
  $(obj)/%.rsi: $(src)/%.rs FORCE
  	$(call if_changed_dep,rustc_rsi_rs)
  
  quiet_cmd_rustc_s_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
-      cmd_rustc_s_rs = $(rust_common_cmd) --emit=asm=$@ $<
+      cmd_rustc_s_rs = $(rust_common_cmd) --emit=asm=$@ $(abspath $<)
  
  $(obj)/%.s: $(src)/%.rs FORCE
  	$(call if_changed_dep,rustc_s_rs)
  
  quiet_cmd_rustc_ll_rs = $(RUSTC_OR_CLIPPY_QUIET) $(quiet_modtag) $@
-      cmd_rustc_ll_rs = $(rust_common_cmd) --emit=llvm-ir=$@ $<
+      cmd_rustc_ll_rs = $(rust_common_cmd) --emit=llvm-ir=$@ $(abspath $<)
  
  $(obj)/%.ll: $(src)/%.rs FORCE
  	$(call if_changed_dep,rustc_ll_rs)




~~ Lina







