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When bazel executions actions in the sandbox, pwd is a path like this: ``` /private/var/tmp/_bazel_ksmiley/92410d0e3373f265902564b48493ac12/sandbox/darwin-sandbox/8/execroot/_main ``` Inside this directory are the inputs, which are symlinks to outside of this pwd: ``` /private/var/tmp/_bazel_ksmiley/92410d0e3373f265902564b48493ac12/sandbox/darwin-sandbox/1/execroot/_main/bazel-out/darwin_arm64-dbg/bin/_objs/main/main.o -> /private/var/tmp/_bazel_ksmiley/92410d0e3373f265902564b48493ac12/execroot/_main/bazel-out/darwin_arm64-dbg/bin/_objs/main/main.o ``` ld64 resolves the absolute path to this object file, including resolving symlinks, _before_ it strips the -oso_prefix argument. Because of this the previous `__BAZEL_EXECUTION_ROOT__` replacement, which was the sandbox pwd, isn't actually a prefix of the canonicalized object file path, leading to -oso_prefix being a no-op, and absolute paths ending up in the binary. I think many folks didn't see this locally because it's common for Apple projects to disable sandboxing for local development for perf reasons, and that's when you're likely to have this debug info in the binary in the first place. With this change we add a new substitution that calculates the sandbox-independent prefix and passes that along instead.
brentleyjones
approved these changes
Sep 30, 2024
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When bazel executions actions in the sandbox, pwd is a path like this:
Inside this directory are the inputs, which are symlinks to outside of
this pwd:
ld64 resolves the absolute path to this object file, including resolving
symlinks, before it strips the -oso_prefix argument. Because of this
the previous
__BAZEL_EXECUTION_ROOT__replacement, which was thesandbox pwd, isn't actually a prefix of the canonicalized object file
path, leading to -oso_prefix being a no-op, and absolute paths ending up
in the binary.
I think many folks didn't see this locally because it's common for Apple
projects to disable sandboxing for local development for perf reasons,
and that's when you're likely to have this debug info in the binary in
the first place.
With this change we add a new substitution that calculates the
sandbox-independent prefix and passes that along instead.