Improve MSVC Crosstool
- Remove `/D_SILENCE_STDEXT_HASH_DEPRECATION_WARNINGS`: it disables warnings for deprecated C++ headers (`<stdext/*>`, `<hash_map>` etc.). Only useful for legacy codebase.
- Remove `/J`: `char` is signed according to ISO C++. There is no reason to make `char` unsigned by default.
- Remove default `/Gy`: moved to feature (`smaller_binary`).
- Remove default `/GF`: string pooling, enabled by default with `/O2`.
- Remove `/DDEBUG` in `dbg` mode: conflict with macros defined in some OSS projects such as LLVM. User should use standard `NDEBUG` to detect debug mode.
Implements a few general `feature` to abstract away details about the compiler:
- `treat_warnings_as_errors`: aka `-Werror`.
- `frame_pointer`: aka `-fno-omit-frame-pointer'.
- `determinism`: redact `__TIME__` macros etc.
- `disable_assertions`: allow user to have `assert/DCHECK` back even in `opt` mode.
- `smaller_binary`: common optimization enabled in `opt` mode. Still allow user to disable it in `opt` (such as when using ASAN).
- `ignore_noisy_warnings`: suppress a bunch of warnings most people don't care. If users want to be pedantic, they can still get those warnings back with `--features=-ignore_noisy_warnings`.
Closes #5519.
PiperOrigin-RevId: 203959555
diff --git a/tools/cpp/CROSSTOOL.tpl b/tools/cpp/CROSSTOOL.tpl
index 0a4b940..abeb2a2 100644
--- a/tools/cpp/CROSSTOOL.tpl
+++ b/tools/cpp/CROSSTOOL.tpl
@@ -211,19 +211,12 @@
# Turn off warning messages.
compiler_flag: "/D_CRT_SECURE_NO_DEPRECATE"
compiler_flag: "/D_CRT_SECURE_NO_WARNINGS"
- compiler_flag: "/D_SILENCE_STDEXT_HASH_DEPRECATION_WARNINGS"
# Useful options to have on for compilation.
# Increase the capacity of object files to 2^32 sections.
compiler_flag: "/bigobj"
# Allocate 500MB for precomputed headers.
compiler_flag: "/Zm500"
- # Use unsigned char by default.
- compiler_flag: "/J"
- # Use function level linking.
- compiler_flag: "/Gy"
- # Use string pooling.
- compiler_flag: "/GF"
# Catch C++ exceptions only and tell the compiler to assume that functions declared
# as extern "C" never throw a C++ exception.
compiler_flag: "/EHsc"
@@ -881,7 +874,6 @@
flag_group {
flag: "/Od"
flag: "/Z7"
- flag: "/DDEBUG"
}
}
flag_set {
@@ -904,7 +896,6 @@
flag_group {
flag: "/Od"
flag: "/Z7"
- flag: "/DDEBUG"
}
}
flag_set {
@@ -925,13 +916,114 @@
action: 'c-compile'
action: 'c++-compile'
flag_group {
- flag: "/O2"
+ flag: "/O2" # Implies /Og /Oi /Ot /Oy /Ob2 /Gs /GF /Gy
+ }
+ }
+ implies: 'frame_pointer'
+ }
+
+ # Keep stack frames for debugging, even in opt mode.
+ # Must come after /O1, /O2 and /Ox.
+ feature {
+ name: "frame_pointer"
+ flag_set {
+ action: "c-compile"
+ action: "c++-compile"
+ flag_group {
+ flag: "/Oy-"
+ }
+ }
+ }
+
+ # Remove assert/DCHECKs in opt mode.
+ # You can have them back with --features=-disable_assertions.
+ feature {
+ name: 'disable_assertions'
+ enabled: true
+ flag_set {
+ action: 'c-compile'
+ action: 'c++-compile'
+ with_feature: {
+ feature: 'opt'
+ }
+ flag_group {
flag: "/DNDEBUG"
}
}
}
feature {
+ name: "determinism"
+ enabled: true
+ flag_set {
+ action: "c-compile"
+ action: "c++-compile"
+ flag_group {
+ # Make C++ compilation deterministic. Use linkstamping instead of these
+ # compiler symbols.
+ # TODO: detect clang on Windows and use "-Wno-builtin-macro-redefined"
+ flag: "/wd4177" # Trying to define or undefine a predefined macro
+ flag: "-D__DATE__=\"redacted\""
+ flag: "-D__TIMESTAMP__=\"redacted\""
+ flag: "-D__TIME__=\"redacted\""
+ }
+ }
+ }
+
+ feature {
+ name: 'treat_warnings_as_errors'
+ flag_set {
+ action: 'c-compile'
+ action: 'c++-compile'
+ flag_group {
+ flag: "/WX"
+ }
+ }
+ }
+
+ # Trade slower build time for smaller binary
+ feature {
+ name: 'smaller_binary'
+ enabled: true
+ flag_set {
+ action: 'c-compile'
+ action: 'c++-compile'
+ with_feature: {
+ feature: 'opt'
+ }
+ flag_group {
+ flag: "/Gy" # Enable function-level linking (-ffunction-sections)
+ flag: "/Gw" # Optimize global data (-fdata-sections)
+ }
+ }
+ flag_set {
+ action: 'c++-link-executable'
+ action: 'c++-link-dynamic-library',
+ action: 'c++-link-nodeps-dynamic-library'
+ with_feature: {
+ feature: 'opt'
+ }
+ flag_group {
+ flag: '/OPT:ICF' # Fold identical functions
+ flag: '/OPT:REF' # Eliminate unreferenced functions and data
+ }
+ }
+ }
+
+ # Suppress warnings that most users do not care
+ feature {
+ name: 'ignore_noisy_warnings'
+ enabled: true
+ flag_set {
+ action: 'c++-link-static-library'
+ flag_group {
+ # Suppress 'object file does not define any public symbols' warning
+ flag: '/ignore:4221'
+ }
+ }
+ }
+
+ feature {
name: 'user_compile_flags'
flag_set {
expand_if_all_available: 'user_compile_flags'
