From f1ff54a10b4abc248b0cfcc5d3c1ebbf534522c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Thi=C3=A9baud=20Weksteen?= <tweek@google.com>
Date: Mon, 22 Mar 2021 14:24:54 +0100
Subject: [PATCH] rust: Drop libgcc dependency

Rustc unstable option "link-native-libraries" is used to prevent the
linkage of other libraries via the #[link] directive. Add a dependency
to libclang_rt.builtins, similarly to cc.

Bug: 141331117
Test: lunch aosp_crosshatch-userdebug; m
Change-Id: I5c232291a5dd08a99e6a12a1295e30bb8e4fcaf1
---
 rust/binary.go           | 2 +-
 rust/bindgen.go          | 2 +-
 rust/compiler.go         | 8 ++++----
 rust/config/global.go    | 3 ++-
 rust/config/toolchain.go | 4 ++++
 rust/library.go          | 2 +-
 6 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/rust/binary.go b/rust/binary.go
index df489169b..dfe8744a1 100644
--- a/rust/binary.go
+++ b/rust/binary.go
@@ -87,7 +87,7 @@ func (binary *binaryDecorator) compilerDeps(ctx DepsContext, deps Deps) Deps {
 	deps = binary.baseCompiler.compilerDeps(ctx, deps)
 
 	if ctx.toolchain().Bionic() {
-		deps = bionicDeps(deps, Bool(binary.Properties.Static_executable))
+		deps = bionicDeps(ctx, deps, Bool(binary.Properties.Static_executable))
 		if Bool(binary.Properties.Static_executable) {
 			deps.CrtBegin = "crtbegin_static"
 		} else {
diff --git a/rust/bindgen.go b/rust/bindgen.go
index db69e2337..bcc26b899 100644
--- a/rust/bindgen.go
+++ b/rust/bindgen.go
@@ -260,7 +260,7 @@ func NewRustBindgen(hod android.HostOrDeviceSupported) (*Module, *bindgenDecorat
 func (b *bindgenDecorator) SourceProviderDeps(ctx DepsContext, deps Deps) Deps {
 	deps = b.BaseSourceProvider.SourceProviderDeps(ctx, deps)
 	if ctx.toolchain().Bionic() {
-		deps = bionicDeps(deps, false)
+		deps = bionicDeps(ctx, deps, false)
 	}
 
 	deps.SharedLibs = append(deps.SharedLibs, b.ClangProperties.Shared_libs...)
diff --git a/rust/compiler.go b/rust/compiler.go
index 98ad7ad1b..200af9061 100644
--- a/rust/compiler.go
+++ b/rust/compiler.go
@@ -281,7 +281,7 @@ func (compiler *baseCompiler) compilerDeps(ctx DepsContext, deps Deps) Deps {
 	return deps
 }
 
-func bionicDeps(deps Deps, static bool) Deps {
+func bionicDeps(ctx DepsContext, deps Deps, static bool) Deps {
 	bionicLibs := []string{}
 	bionicLibs = append(bionicLibs, "liblog")
 	bionicLibs = append(bionicLibs, "libc")
@@ -294,9 +294,9 @@ func bionicDeps(deps Deps, static bool) Deps {
 		deps.SharedLibs = append(deps.SharedLibs, bionicLibs...)
 	}
 
-	//TODO(b/141331117) libstd requires libgcc on Android
-	deps.StaticLibs = append(deps.StaticLibs, "libgcc")
-
+	if libRuntimeBuiltins := config.BuiltinsRuntimeLibrary(ctx.toolchain()); libRuntimeBuiltins != "" {
+		deps.StaticLibs = append(deps.StaticLibs, libRuntimeBuiltins)
+	}
 	return deps
 }
 
diff --git a/rust/config/global.go b/rust/config/global.go
index 12f49728c..9208ddb69 100644
--- a/rust/config/global.go
+++ b/rust/config/global.go
@@ -53,6 +53,7 @@ var (
 
 	deviceGlobalRustFlags = []string{
 		"-C panic=abort",
+		"-Z link-native-libraries=no",
 	}
 
 	deviceGlobalLinkFlags = []string{
@@ -62,7 +63,7 @@ var (
 		// Override cc's --no-undefined-version to allow rustc's generated alloc functions
 		"-Wl,--undefined-version",
 
-		"-Bdynamic",
+		"-Wl,-Bdynamic",
 		"-nostdlib",
 		"-Wl,--pack-dyn-relocs=android+relr",
 		"-Wl,--use-android-relr-tags",
diff --git a/rust/config/toolchain.go b/rust/config/toolchain.go
index 9525c38aa..a769f121c 100644
--- a/rust/config/toolchain.go
+++ b/rust/config/toolchain.go
@@ -112,6 +112,10 @@ func (toolchainBase) LibclangRuntimeLibraryArch() string {
 	return ""
 }
 
+func BuiltinsRuntimeLibrary(t Toolchain) string {
+	return LibclangRuntimeLibrary(t, "builtins")
+}
+
 func LibFuzzerRuntimeLibrary(t Toolchain) string {
 	return LibclangRuntimeLibrary(t, "fuzzer")
 }
diff --git a/rust/library.go b/rust/library.go
index 7ff13ec66..71fe1f538 100644
--- a/rust/library.go
+++ b/rust/library.go
@@ -404,7 +404,7 @@ func (library *libraryDecorator) compilerDeps(ctx DepsContext, deps Deps) Deps {
 	deps = library.baseCompiler.compilerDeps(ctx, deps)
 
 	if ctx.toolchain().Bionic() && (library.dylib() || library.shared()) {
-		deps = bionicDeps(deps, false)
+		deps = bionicDeps(ctx, deps, false)
 		deps.CrtBegin = "crtbegin_so"
 		deps.CrtEnd = "crtend_so"
 	}