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

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This commit is contained in:
Krzysztof Kosiński
2023-10-02 22:27:21 +00:00
committed by Gerrit Code Review
parent e298d42044 1a4572ec9c
commit eae6635a0f
1 changed files with 121 additions and 78 deletions
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199
cc/config/global.go
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@@ -29,83 +29,112 @@ var (
// Flags used by lots of devices. Putting them in package static variables // 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 // will save bytes in build.ninja so they aren't repeated for every file
commonGlobalCflags = []string{ commonGlobalCflags = []string{
"-DANDROID", // Enable some optimization by default.
"-fmessage-length=0", "-O2",
"-W",
// Warnings enabled by default. Reference:
// https://clang.llvm.org/docs/DiagnosticsReference.html
"-Wall", "-Wall",
"-Wno-unused", "-Wextra",
"-Winit-self", "-Winit-self",
"-Wpointer-arith", "-Wpointer-arith",
"-Wunreachable-code-loop-increment", "-Wunguarded-availability",
// Make paths in deps files relative // Warnings treated as errors by default.
"-no-canonical-prefixes", // See also noOverrideGlobalCflags for errors that cannot be disabled
// from Android.bp files.
"-DNDEBUG",
"-UDEBUG",
"-fno-exceptions",
"-O2",
"-fdebug-default-version=5",
"-fno-strict-aliasing",
// Using __DATE__/__TIME__ causes build nondeterminism.
"-Werror=date-time", "-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", "-Werror=pragma-pack",
// Same as above, but detects alignment pragmas around a header
// inclusion.
"-Werror=pragma-pack-suspicious-include", "-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", "-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", "-Werror=unreachable-code-loop-increment",
// Force deprecation warnings to be warnings for code that compiles with -Werror. // 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",
// 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", "-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 // 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. // not emit the table by default on Android since NDK still uses GNU binutils.
"-faddrsig", "-faddrsig",
// Help catch common 32/64-bit errors. // Emit debugging data in a modern format (DWARF v5).
"-Werror=int-conversion", "-fdebug-default-version=5",
// Force clang to always output color diagnostics. Ninja will strip the ANSI // Force clang to always output color diagnostics. Ninja will strip the ANSI
// color codes if it is not running in a terminal. // color codes if it is not running in a terminal.
"-fcolor-diagnostics", "-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",
// http://b/145210666
"-Wno-error=reorder-init-list",
// 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__",
// Turn off FMA which got enabled by default in clang-r445002 (http://b/218805949) // Turn off FMA which got enabled by default in clang-r445002 (http://b/218805949)
"-ffp-contract=off", "-ffp-contract=off",
// Google C++ style does not allow exceptions, turn them off by default.
"-fno-exceptions",
// 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",
// 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. // Using simple template names reduces the size of debug builds.
"-gsimple-template-names", "-gsimple-template-names",
// Make paths in deps files relative.
"-no-canonical-prefixes",
} }
commonGlobalConlyflags = []string{} commonGlobalConlyflags = []string{}
@@ -117,6 +146,7 @@ var (
"-fdebug-default-version=4", "-fdebug-default-version=4",
} }
// Compilation flags for device code; not applied to host code.
deviceGlobalCflags = []string{ deviceGlobalCflags = []string{
"-ffunction-sections", "-ffunction-sections",
"-fdata-sections", "-fdata-sections",
@@ -152,6 +182,7 @@ var (
"-fvisibility-inlines-hidden", "-fvisibility-inlines-hidden",
} }
// Linking flags for device code; not applied to host binaries.
deviceGlobalLdflags = []string{ deviceGlobalLdflags = []string{
"-Wl,-z,noexecstack", "-Wl,-z,noexecstack",
"-Wl,-z,relro", "-Wl,-z,relro",
@@ -194,6 +225,14 @@ var (
// These flags are appended after the module's cflags, so they cannot be // These flags are appended after the module's cflags, so they cannot be
// overridden from Android.bp files. // 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{ noOverrideGlobalCflags = []string{
"-Werror=bool-operation", "-Werror=bool-operation",
"-Werror=format-insufficient-args", "-Werror=format-insufficient-args",
@@ -245,35 +284,9 @@ var (
noOverride64GlobalCflags = []string{} noOverride64GlobalCflags = []string{}
// Similar to noOverrideGlobalCflags, but applies only to third-party code // Extra cflags applied to third-party code (anything for which
// (anything for which IsThirdPartyPath() in build/soong/android/paths.go // IsThirdPartyPath() in build/soong/android/paths.go returns true;
// returns true - includes external/, most of vendor/ and most of hardware/) // 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.
extraExternalCflags = []string{ extraExternalCflags = []string{
"-Wno-enum-compare", "-Wno-enum-compare",
"-Wno-enum-compare-switch", "-Wno-enum-compare-switch",
@@ -303,11 +316,41 @@ var (
"-Wno-deprecated-non-prototype", "-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{ llvmNextExtraCommonGlobalCflags = []string{
// Do not report warnings when testing with the top of trunk LLVM. // Do not report warnings when testing with the top of trunk LLVM.
"-Wno-error", "-Wno-error",
} }
// Flags that must not appear in any command line.
IllegalFlags = []string{ IllegalFlags = []string{
"-w", "-w",
} }