Merge "More documentation for C++ global config." into main

	// Flags used by lots of devices.  Putting them in package static variables

	// will save bytes in build.ninja so they aren't repeated for every file

	commonGlobalCflags = []string{

		"-DANDROID",

		"-fmessage-length=0",

		"-W",

		// Enable some optimization by default.

		"-O2",

		// Warnings enabled by default. Reference:

		// https://clang.llvm.org/docs/DiagnosticsReference.html

		"-Wall",

		"-Wno-unused",

		"-Wextra",

		"-Winit-self",

		"-Wpointer-arith",

		"-Wunreachable-code-loop-increment",

		// Make paths in deps files relative

		"-no-canonical-prefixes",

		"-DNDEBUG",

		"-UDEBUG",

		"-fno-exceptions",

		"-O2",

		"-fdebug-default-version=5",

		"-Wunguarded-availability",

		"-fno-strict-aliasing",

		// Warnings treated as errors by default.

		// See also noOverrideGlobalCflags for errors that cannot be disabled

		// from Android.bp files.

		// Using __DATE__/__TIME__ causes build nondeterminism.

		"-Werror=date-time",

		// Detects forgotten */& that usually cause a crash

		"-Werror=int-conversion",

		// Detects unterminated alignment modification pragmas, which often lead

		// to ABI mismatch between modules and hard-to-debug crashes.

		"-Werror=pragma-pack",

		// Same as above, but detects alignment pragmas around a header

		// inclusion.

		"-Werror=pragma-pack-suspicious-include",

		// Detects dividing an array size by itself, which is a common typo that

		// leads to bugs.

		"-Werror=sizeof-array-div",

		// Detects a typo that cuts off a prefix from a string literal.

		"-Werror=string-plus-int",

		// Detects for loops that will never execute more than once (for example

		// due to unconditional break), but have a non-empty loop increment

		// clause. Often a mistake/bug.

		"-Werror=unreachable-code-loop-increment",

		// Force deprecation warnings to be warnings for code that compiles with -Werror.

		// Making deprecated usages an error causes extreme pain when trying to deprecate anything.

		// Warnings that should not be errors even for modules with -Werror.

		// Making deprecated usages an error causes extreme pain when trying to

		// deprecate anything.

		"-Wno-error=deprecated-declarations",

		// This rarely indicates a bug. http://b/145210666

		"-Wno-error=reorder-init-list",

		// Warnings disabled by default.

		// Designated initializer syntax is recommended by the Google C++ style

		// and is OK to use even if not formally supported by the chosen C++

		// version.

		"-Wno-c99-designator",

		// Detects uses of a GNU C extension equivalent to a limited form of

		// constexpr. Enabling this would require replacing many constants with

		// macros, which is not a good trade-off.

		"-Wno-gnu-folding-constant",

		// AIDL generated code redeclares pure virtual methods in each

		// subsequent version of an interface, so this warning is currently

		// infeasible to enable.

		"-Wno-inconsistent-missing-override",

		// Incompatible with the Google C++ style guidance to use 'int' for loop

		// indices; poor signal to noise ratio.

		"-Wno-sign-compare",

		// Poor signal to noise ratio.

		"-Wno-unused",

		// Global preprocessor constants.

		"-DANDROID",

		"-DNDEBUG",

		"-UDEBUG",

		"-D__compiler_offsetof=__builtin_offsetof",

		// Allows the bionic versioning.h to indirectly determine whether the

		// option -Wunguarded-availability is on or not.

		"-D__ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__",

		// -f and -g options.

		// Emit address-significance table which allows linker to perform safe ICF. Clang does

		// not emit the table by default on Android since NDK still uses GNU binutils.

		"-faddrsig",

		// Help catch common 32/64-bit errors.

		"-Werror=int-conversion",

		// Emit debugging data in a modern format (DWARF v5).

		"-fdebug-default-version=5",

		// Force clang to always output color diagnostics. Ninja will strip the ANSI

		// color codes if it is not running in a terminal.

		"-fcolor-diagnostics",

		// -Wno-sign-compare is incompatible with the Google C++ style guidance

		// to use 'int' for loop indices, and the signal to noise ratio is poor

		// anyway.

		"-Wno-sign-compare",

		// AIDL generated code redeclares pure virtual methods in each

		// subsequent version of an interface, so this is currently infeasible

		// to enable.

		"-Wno-inconsistent-missing-override",

		// Designated initializer syntax is recommended by the Google C++ style

		// guide and should not be a warning, at least by default.

		"-Wno-c99-designator",

		// Warnings from clang-12

		"-Wno-gnu-folding-constant",

		// Turn off FMA which got enabled by default in clang-r445002 (http://b/218805949)

		"-ffp-contract=off",

		// http://b/145210666

		"-Wno-error=reorder-init-list",

		// Google C++ style does not allow exceptions, turn them off by default.

		"-fno-exceptions",

		// Calls to the APIs that are newer than the min sdk version of the caller should be

		// guarded with __builtin_available.

		"-Wunguarded-availability",

		// This macro allows the bionic versioning.h to indirectly determine whether the

		// option -Wunguarded-availability is on or not.

		"-D__ANDROID_UNAVAILABLE_SYMBOLS_ARE_WEAK__",

		// Disable optimizations based on strict aliasing by default.

		// The performance benefit of enabling them currently does not outweigh

		// the risk of hard-to-reproduce bugs.

		"-fno-strict-aliasing",

		// Turn off FMA which got enabled by default in clang-r445002 (http://b/218805949)

		"-ffp-contract=off",

		// Disable line wrapping for error messages - it interferes with

		// displaying logs in web browsers.

		"-fmessage-length=0",

		// Using simple template names reduces the size of debug builds.

		"-gsimple-template-names",

		// Make paths in deps files relative.

		"-no-canonical-prefixes",

	}

	commonGlobalConlyflags = []string{}

		"-fdebug-default-version=4",

	}

	// Compilation flags for device code; not applied to host code.

	deviceGlobalCflags = []string{

		"-ffunction-sections",

		"-fdata-sections",

		"-fvisibility-inlines-hidden",

	}

	// Linking flags for device code; not applied to host binaries.

	deviceGlobalLdflags = []string{

		"-Wl,-z,noexecstack",

		"-Wl,-z,relro",

	// These flags are appended after the module's cflags, so they cannot be

	// overridden from Android.bp files.

	//

	// NOTE: if you need to disable a warning to unblock a compiler upgrade

	// and it is only triggered by third party code, add it to

	// extraExternalCflags (if possible) or noOverrideExternalGlobalCflags

	// (if the former doesn't work). If the new warning also occurs in first

	// party code, try adding it to commonGlobalCflags first. Adding it here

	// should be the last resort, because it prevents all code in Android from

	// opting into the warning.

	noOverrideGlobalCflags = []string{

		"-Werror=bool-operation",

		"-Werror=format-insufficient-args",

	noOverride64GlobalCflags = []string{}

	// Similar to noOverrideGlobalCflags, but applies only to third-party code

	// (anything for which IsThirdPartyPath() in build/soong/android/paths.go

	// returns true - includes external/, most of vendor/ and most of hardware/)

	noOverrideExternalGlobalCflags = []string{

		// http://b/151457797

		"-fcommon",

		// http://b/191699019

		"-Wno-format-insufficient-args",

		// http://b/296321145

		// Indicates potential memory or stack corruption, so should be changed

		// to a hard error. Currently triggered by some vendor code.

		"-Wno-incompatible-function-pointer-types",

		// http://b/296321508

		// Introduced in response to a critical security vulnerability and

		// should be a hard error - it requires only whitespace changes to fix.

		"-Wno-misleading-indentation",

		// Triggered by old LLVM code in external/llvm. Likely not worth

		// enabling since it's a cosmetic issue.

		"-Wno-bitwise-instead-of-logical",

		"-Wno-unused-but-set-variable",

		"-Wno-unused-but-set-parameter",

		"-Wno-unqualified-std-cast-call",

		"-Wno-array-parameter",

		"-Wno-gnu-offsetof-extensions",

	}

	// Extra cflags for external third-party projects to disable warnings that

	// are infeasible to fix in all the external projects and their upstream repos.

	// Extra cflags applied to third-party code (anything for which

	// IsThirdPartyPath() in build/soong/android/paths.go returns true;

	// includes external/, most of vendor/ and most of hardware/)

	extraExternalCflags = []string{

		"-Wno-enum-compare",

		"-Wno-enum-compare-switch",

		"-Wno-deprecated-non-prototype",

	}

	// Similar to noOverrideGlobalCflags, but applies only to third-party code

	// (see extraExternalCflags).

	// This section can unblock compiler upgrades when a third party module that

	// enables -Werror and some group of warnings explicitly triggers newly

	// added warnings.

	noOverrideExternalGlobalCflags = []string{

		// http://b/151457797

		"-fcommon",

		// http://b/191699019

		"-Wno-format-insufficient-args",

		// http://b/296321145

		// Indicates potential memory or stack corruption, so should be changed

		// to a hard error. Currently triggered by some vendor code.

		"-Wno-incompatible-function-pointer-types",

		// http://b/296321508

		// Introduced in response to a critical security vulnerability and

		// should be a hard error - it requires only whitespace changes to fix.

		"-Wno-misleading-indentation",

		// Triggered by old LLVM code in external/llvm. Likely not worth

		// enabling since it's a cosmetic issue.

		"-Wno-bitwise-instead-of-logical",

		"-Wno-unused-but-set-variable",

		"-Wno-unused-but-set-parameter",

		"-Wno-unqualified-std-cast-call",

		"-Wno-array-parameter",

		"-Wno-gnu-offsetof-extensions",

	}

	llvmNextExtraCommonGlobalCflags = []string{

		// Do not report warnings when testing with the top of trunk LLVM.

		"-Wno-error",

	}

	// Flags that must not appear in any command line.

	IllegalFlags = []string{

		"-w",

	}