rust: Fix coverage in no-std crates

Coverage builds for no_std crates currently fail because
profiler_builtins are part of libstd and therefore do not get included.

When calculating the dependencies for coverage enabled targets, check if
the stdlib is being included, and if it is not then pull the
profiler_builtins sysroot.

Bug: 249551848
Test: CLANG_COVERAGE=true NATIVE_COVERAGE_PATHS='*' make libtinyvec_nostd.rlib-std
Change-Id: I73f89bddcb2d4d9c704cb3962ee39b73888c7f3f

1 files changed, 13 insertions, 0 deletions

diff --git a/rust/coverage.go b/rust/coverage.go
index 5ea481fcf..bc6504ddc 100644
--- a/rust/coverage.go
+++ b/rust/coverage.go
@@ -21,6 +21,7 @@ import (
 )
 
 var CovLibraryName = "libprofile-clang-extras"
+var ProfilerBuiltins = "libprofiler_builtins.rust_sysroot"
 
 // Add '%c' to default specifier after we resolve http://b/210012154
 const profileInstrFlag = "-fprofile-instr-generate=/data/misc/trace/clang-%p-%m.profraw"
@@ -41,6 +42,11 @@ func (cov *coverage) deps(ctx DepsContext, deps Deps) Deps {
 		ctx.AddVariationDependencies([]blueprint.Variation{
 			{Mutator: "link", Variation: "static"},
 		}, cc.CoverageDepTag, CovLibraryName)
+
+		// no_std modules are missing libprofiler_builtins which provides coverage, so we need to add it as a dependency.
+		if rustModule, ok := ctx.Module().(*Module); ok && rustModule.compiler.noStdlibs() {
+			ctx.AddVariationDependencies([]blueprint.Variation{{Mutator: "rust_libraries", Variation: "rlib"}}, rlibDepTag, ProfilerBuiltins)
+		}
 	}
 
 	return deps
@@ -60,6 +66,13 @@ func (cov *coverage) flags(ctx ModuleContext, flags Flags, deps PathDeps) (Flags
 		flags.LinkFlags = append(flags.LinkFlags,
 			profileInstrFlag, "-g", coverage.OutputFile().Path().String(), "-Wl,--wrap,open")
 		deps.StaticLibs = append(deps.StaticLibs, coverage.OutputFile().Path())
+
+		// no_std modules are missing libprofiler_builtins which provides coverage, so we need to add it as a dependency.
+		if rustModule, ok := ctx.Module().(*Module); ok && rustModule.compiler.noStdlibs() {
+			profiler_builtins := ctx.GetDirectDepWithTag(ProfilerBuiltins, rlibDepTag).(*Module)
+			deps.RLibs = append(deps.RLibs, RustLibrary{Path: profiler_builtins.OutputFile().Path(), CrateName: profiler_builtins.CrateName()})
+		}
+
 		if cc.EnableContinuousCoverage(ctx) {
 			flags.RustFlags = append(flags.RustFlags, "-C llvm-args=--runtime-counter-relocation")
 			flags.LinkFlags = append(flags.LinkFlags, "-Wl,-mllvm,-runtime-counter-relocation")