cc: Pull out common library compilation flags

In preparation for building stubs from Rust, refactor how compilation
flags are calculated by pulling the common compilation flags out of
decorator-specific flags functions so they can be reused when building
stubs from Rust modules.

Bug: 203478530
Test: m blueprint_tests
Change-Id: If7a644ea3105d3fb8b2b5110b4f07ca053d1c5a3
diff --git a/cc/compiler.go b/cc/compiler.go
index d237c6e..1899f59 100644
--- a/cc/compiler.go
+++ b/cc/compiler.go
@@ -360,6 +360,29 @@
 	}
 }
 
+func addTargetFlags(ctx android.ModuleContext, flags Flags, tc config.Toolchain, version string, bpf bool) Flags {
+	target := "-target " + tc.ClangTriple()
+	if ctx.Os().Class == android.Device {
+		if version == "" || version == "current" {
+			target += strconv.Itoa(android.FutureApiLevelInt)
+		} else {
+			apiLevel := nativeApiLevelOrPanic(ctx, version)
+			target += strconv.Itoa(apiLevel.FinalOrFutureInt())
+		}
+	}
+
+	// bpf targets don't need the default target triple. b/308826679
+	if bpf {
+		target = "--target=bpf"
+	}
+
+	flags.Global.CFlags = append(flags.Global.CFlags, target)
+	flags.Global.AsFlags = append(flags.Global.AsFlags, target)
+	flags.Global.LdFlags = append(flags.Global.LdFlags, target)
+
+	return flags
+}
+
 // Create a Flags struct that collects the compile flags from global values,
 // per-target values, module type values, and per-module Blueprints properties
 func (compiler *baseCompiler) compilerFlags(ctx ModuleContext, flags Flags, deps PathDeps) Flags {
@@ -513,25 +536,7 @@
 	flags.Local.ConlyFlags = config.ClangFilterUnknownCflags(flags.Local.ConlyFlags)
 	flags.Local.LdFlags = config.ClangFilterUnknownCflags(flags.Local.LdFlags)
 
-	target := "-target " + tc.ClangTriple()
-	if ctx.Os().Class == android.Device {
-		version := ctx.minSdkVersion()
-		if version == "" || version == "current" {
-			target += strconv.Itoa(android.FutureApiLevelInt)
-		} else {
-			apiLevel := nativeApiLevelOrPanic(ctx, version)
-			target += strconv.Itoa(apiLevel.FinalOrFutureInt())
-		}
-	}
-
-	// bpf targets don't need the default target triple. b/308826679
-	if proptools.Bool(compiler.Properties.Bpf_target) {
-		target = "--target=bpf"
-	}
-
-	flags.Global.CFlags = append(flags.Global.CFlags, target)
-	flags.Global.AsFlags = append(flags.Global.AsFlags, target)
-	flags.Global.LdFlags = append(flags.Global.LdFlags, target)
+	flags = addTargetFlags(ctx, flags, tc, ctx.minSdkVersion(), Bool(compiler.Properties.Bpf_target))
 
 	hod := "Host"
 	if ctx.Os().Class == android.Device {
diff --git a/cc/library.go b/cc/library.go
index b218bce..7b225ec 100644
--- a/cc/library.go
+++ b/cc/library.go
@@ -25,6 +25,7 @@
 	"sync"
 
 	"android/soong/android"
+	"android/soong/cc/config"
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/depset"
@@ -459,11 +460,15 @@
 	return props
 }
 
-// linkerFlags takes a Flags struct and augments it to contain linker flags that are defined by this
-// library, or that are implied by attributes of this library (such as whether this library is a
-// shared library).
-func (library *libraryDecorator) linkerFlags(ctx ModuleContext, flags Flags) Flags {
-	flags = library.baseLinker.linkerFlags(ctx, flags)
+func commonLibraryLinkerFlags(ctx android.ModuleContext, flags Flags,
+	toolchain config.Toolchain, libName string) Flags {
+
+	mod, ok := ctx.Module().(LinkableInterface)
+
+	if !ok {
+		ctx.ModuleErrorf("trying to add linker flags to a non-LinkableInterface module.")
+		return flags
+	}
 
 	// MinGW spits out warnings about -fPIC even for -fpie?!) being ignored because
 	// all code is position independent, and then those warnings get promoted to
@@ -471,27 +476,18 @@
 	if !ctx.Windows() {
 		flags.Global.CFlags = append(flags.Global.CFlags, "-fPIC")
 	}
-
-	if library.static() {
-		flags.Local.CFlags = append(flags.Local.CFlags, library.StaticProperties.Static.Cflags.GetOrDefault(ctx, nil)...)
-	} else if library.shared() {
-		flags.Local.CFlags = append(flags.Local.CFlags, library.SharedProperties.Shared.Cflags.GetOrDefault(ctx, nil)...)
-	}
-
-	if library.shared() {
-		libName := library.getLibName(ctx)
+	if mod.Shared() {
 		var f []string
-		if ctx.toolchain().Bionic() {
+		if toolchain.Bionic() {
 			f = append(f,
 				"-nostdlib",
 				"-Wl,--gc-sections",
 			)
 		}
-
 		if ctx.Darwin() {
 			f = append(f,
 				"-dynamiclib",
-				"-install_name @rpath/"+libName+flags.Toolchain.ShlibSuffix(),
+				"-install_name @rpath/"+libName+toolchain.ShlibSuffix(),
 			)
 			if ctx.Arch().ArchType == android.X86 {
 				f = append(f,
@@ -501,16 +497,30 @@
 		} else {
 			f = append(f, "-shared")
 			if !ctx.Windows() {
-				f = append(f, "-Wl,-soname,"+libName+flags.Toolchain.ShlibSuffix())
+				f = append(f, "-Wl,-soname,"+libName+toolchain.ShlibSuffix())
 			}
 		}
-
 		flags.Global.LdFlags = append(flags.Global.LdFlags, f...)
 	}
 
 	return flags
 }
 
+// linkerFlags takes a Flags struct and augments it to contain linker flags that are defined by this
+// library, or that are implied by attributes of this library (such as whether this library is a
+// shared library).
+func (library *libraryDecorator) linkerFlags(ctx ModuleContext, flags Flags) Flags {
+	flags = library.baseLinker.linkerFlags(ctx, flags)
+	flags = commonLibraryLinkerFlags(ctx, flags, ctx.toolchain(), library.getLibName(ctx))
+	if library.static() {
+		flags.Local.CFlags = append(flags.Local.CFlags, library.StaticProperties.Static.Cflags.GetOrDefault(ctx, nil)...)
+	} else if library.shared() {
+		flags.Local.CFlags = append(flags.Local.CFlags, library.SharedProperties.Shared.Cflags.GetOrDefault(ctx, nil)...)
+	}
+
+	return flags
+}
+
 // compilerFlags takes a Flags and augments it to contain compile flags from global values,
 // per-target values, module type values, per-module Blueprints properties, extra flags from
 // `flags`, and generated sources from `deps`.
diff --git a/cc/linker.go b/cc/linker.go
index 159bca4..20c2f4a 100644
--- a/cc/linker.go
+++ b/cc/linker.go
@@ -471,16 +471,77 @@
 
 // ModuleContext extends BaseModuleContext
 // BaseModuleContext should know if LLD is used?
-func (linker *baseLinker) linkerFlags(ctx ModuleContext, flags Flags) Flags {
-	toolchain := ctx.toolchain()
-
+func commonLinkerFlags(ctx android.ModuleContext, flags Flags, useClangLld bool,
+	toolchain config.Toolchain, allow_undefined_symbols bool) Flags {
 	hod := "Host"
 	if ctx.Os().Class == android.Device {
 		hod = "Device"
 	}
 
-	if linker.useClangLld(ctx) {
+	mod, ok := ctx.Module().(LinkableInterface)
+	if !ok {
+		ctx.ModuleErrorf("trying to add commonLinkerFlags to non-LinkableInterface module.")
+		return flags
+	}
+	if useClangLld {
 		flags.Global.LdFlags = append(flags.Global.LdFlags, fmt.Sprintf("${config.%sGlobalLldflags}", hod))
+	} else {
+		flags.Global.LdFlags = append(flags.Global.LdFlags, fmt.Sprintf("${config.%sGlobalLdflags}", hod))
+	}
+
+	if allow_undefined_symbols {
+		if ctx.Darwin() {
+			// darwin defaults to treating undefined symbols as errors
+			flags.Global.LdFlags = append(flags.Global.LdFlags, "-Wl,-undefined,dynamic_lookup")
+		}
+	} else if !ctx.Darwin() && !ctx.Windows() {
+		flags.Global.LdFlags = append(flags.Global.LdFlags, "-Wl,--no-undefined")
+	}
+
+	if useClangLld {
+		flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.Lldflags())
+	} else {
+		flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.Ldflags())
+	}
+
+	if !toolchain.Bionic() && ctx.Os() != android.LinuxMusl {
+		if !ctx.Windows() {
+			// Add -ldl, -lpthread, -lm and -lrt to host builds to match the default behavior of device
+			// builds
+			flags.Global.LdFlags = append(flags.Global.LdFlags,
+				"-ldl",
+				"-lpthread",
+				"-lm",
+			)
+			if !ctx.Darwin() {
+				flags.Global.LdFlags = append(flags.Global.LdFlags, "-lrt")
+			}
+		}
+	}
+	staticLib := mod.CcLibraryInterface() && mod.Static()
+	if ctx.Host() && !ctx.Windows() && !staticLib {
+		flags.Global.LdFlags = append(flags.Global.LdFlags, RpathFlags(ctx)...)
+	}
+
+	flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.ToolchainLdflags())
+	return flags
+}
+
+func (linker *baseLinker) linkerFlags(ctx ModuleContext, flags Flags) Flags {
+	toolchain := ctx.toolchain()
+	allow_undefined_symbols := Bool(linker.Properties.Allow_undefined_symbols)
+
+	flags = commonLinkerFlags(ctx, flags, linker.useClangLld(ctx), toolchain,
+		allow_undefined_symbols)
+
+	if !toolchain.Bionic() && ctx.Os() != android.LinuxMusl {
+		CheckBadHostLdlibs(ctx, "host_ldlibs", linker.Properties.Host_ldlibs)
+		flags.Local.LdFlags = append(flags.Local.LdFlags, linker.Properties.Host_ldlibs...)
+	}
+
+	CheckBadLinkerFlags(ctx, "ldflags", linker.Properties.Ldflags)
+
+	if linker.useClangLld(ctx) {
 		if !BoolDefault(linker.Properties.Pack_relocations, packRelocationsDefault) {
 			flags.Global.LdFlags = append(flags.Global.LdFlags, "-Wl,--pack-dyn-relocs=none")
 		} else if ctx.Device() {
@@ -498,53 +559,10 @@
 				flags.Global.LdFlags = append(flags.Global.LdFlags, "-Wl,--pack-dyn-relocs=android")
 			}
 		}
-	} else {
-		flags.Global.LdFlags = append(flags.Global.LdFlags, fmt.Sprintf("${config.%sGlobalLdflags}", hod))
 	}
-	if Bool(linker.Properties.Allow_undefined_symbols) {
-		if ctx.Darwin() {
-			// darwin defaults to treating undefined symbols as errors
-			flags.Global.LdFlags = append(flags.Global.LdFlags, "-Wl,-undefined,dynamic_lookup")
-		}
-	} else if !ctx.Darwin() && !ctx.Windows() {
-		flags.Global.LdFlags = append(flags.Global.LdFlags, "-Wl,--no-undefined")
-	}
-
-	if linker.useClangLld(ctx) {
-		flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.Lldflags())
-	} else {
-		flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.Ldflags())
-	}
-
-	if !ctx.toolchain().Bionic() && ctx.Os() != android.LinuxMusl {
-		CheckBadHostLdlibs(ctx, "host_ldlibs", linker.Properties.Host_ldlibs)
-
-		flags.Local.LdFlags = append(flags.Local.LdFlags, linker.Properties.Host_ldlibs...)
-
-		if !ctx.Windows() {
-			// Add -ldl, -lpthread, -lm and -lrt to host builds to match the default behavior of device
-			// builds
-			flags.Global.LdFlags = append(flags.Global.LdFlags,
-				"-ldl",
-				"-lpthread",
-				"-lm",
-			)
-			if !ctx.Darwin() {
-				flags.Global.LdFlags = append(flags.Global.LdFlags, "-lrt")
-			}
-		}
-	}
-
-	CheckBadLinkerFlags(ctx, "ldflags", linker.Properties.Ldflags)
 
 	flags.Local.LdFlags = append(flags.Local.LdFlags, proptools.NinjaAndShellEscapeList(linker.Properties.Ldflags)...)
 
-	if ctx.Host() && !ctx.Windows() && !ctx.static() {
-		flags.Global.LdFlags = append(flags.Global.LdFlags, RpathFlags(ctx)...)
-	}
-
-	flags.Global.LdFlags = append(flags.Global.LdFlags, toolchain.ToolchainLdflags())
-
 	// Version_script is not needed when linking stubs lib where the version
 	// script is created from the symbol map file.
 	if !linker.dynamicProperties.BuildStubs {