[CMake] Set correct flags for clang-cl (#278)

clang-cl produce binaries with MSVC ABI and wants to be as flag-compatible with pure MSVC as possible, so this leads to all sorts of weird cases.

clang-cl alias /Wall as clang's -Weverything which is way too verbose, so it needs /W3 like pure MSVC.
clang-cl only understand GCC style warning flags (-W[no]blah) and just silent drop MSVC style warning flags (/wd[num]).
clang-cl needs MSVC define flags since it is consuming the same header files as pure MSVC.
CMake set CMAKE_CXX_COMPILER_ID as Clang when clang-cl is detected, so need extra if (MSVC) to differentiate it.

We are not doing clang-cl specialization in Bazel as currently there is no reliable way to detect clang-cl in Bazel..

This PR should be NFC for LLVM/GCC users on Unix platforms.

Other changes:

Add ABSL_ prefix to variable names to avoid name collision in CMake.

1 files changed, 90 insertions, 14 deletions

diff --git a/absl/copts/GENERATED_AbseilCopts.cmake b/absl/copts/GENERATED_AbseilCopts.cmake
index d02ea193..9031bfa5 100644
--- a/absl/copts/GENERATED_AbseilCopts.cmake
+++ b/absl/copts/GENERATED_AbseilCopts.cmake
@@ -3,11 +3,87 @@
 # (1) Edit absl/copts/copts.py.
 # (2) Run `python <path_to_absl>/copts/generate_copts.py`.
 
-list(APPEND GCC_EXCEPTIONS_FLAGS
+list(APPEND ABSL_CLANG_CL_EXCEPTIONS_FLAGS
+    "/U_HAS_EXCEPTIONS"
+    "/D_HAS_EXCEPTIONS=1"
+    "/EHsc"
+)
+
+list(APPEND ABSL_CLANG_CL_FLAGS
+    "/W3"
+    "-Wno-c++98-compat-pedantic"
+    "-Wno-conversion"
+    "-Wno-covered-switch-default"
+    "-Wno-deprecated"
+    "-Wno-disabled-macro-expansion"
+    "-Wno-double-promotion"
+    "-Wno-comma"
+    "-Wno-extra-semi"
+    "-Wno-extra-semi-stmt"
+    "-Wno-packed"
+    "-Wno-padded"
+    "-Wno-sign-compare"
+    "-Wno-float-conversion"
+    "-Wno-float-equal"
+    "-Wno-format-nonliteral"
+    "-Wno-gcc-compat"
+    "-Wno-global-constructors"
+    "-Wno-exit-time-destructors"
+    "-Wno-nested-anon-types"
+    "-Wno-non-modular-include-in-module"
+    "-Wno-old-style-cast"
+    "-Wno-range-loop-analysis"
+    "-Wno-reserved-id-macro"
+    "-Wno-shorten-64-to-32"
+    "-Wno-switch-enum"
+    "-Wno-thread-safety-negative"
+    "-Wno-undef"
+    "-Wno-unknown-warning-option"
+    "-Wno-unreachable-code"
+    "-Wno-unused-macros"
+    "-Wno-weak-vtables"
+    "-Wbitfield-enum-conversion"
+    "-Wbool-conversion"
+    "-Wconstant-conversion"
+    "-Wenum-conversion"
+    "-Wint-conversion"
+    "-Wliteral-conversion"
+    "-Wnon-literal-null-conversion"
+    "-Wnull-conversion"
+    "-Wobjc-literal-conversion"
+    "-Wno-sign-conversion"
+    "-Wstring-conversion"
+    "/DNOMINMAX"
+    "/DWIN32_LEAN_AND_MEAN"
+    "/D_CRT_SECURE_NO_WARNINGS"
+    "/D_SCL_SECURE_NO_WARNINGS"
+    "/D_ENABLE_EXTENDED_ALIGNED_STORAGE"
+)
+
+list(APPEND ABSL_CLANG_CL_TEST_FLAGS
+    "-Wno-c99-extensions"
+    "-Wno-missing-noreturn"
+    "-Wno-missing-prototypes"
+    "-Wno-missing-variable-declarations"
+    "-Wno-null-conversion"
+    "-Wno-shadow"
+    "-Wno-shift-sign-overflow"
+    "-Wno-sign-compare"
+    "-Wno-unused-function"
+    "-Wno-unused-member-function"
+    "-Wno-unused-parameter"
+    "-Wno-unused-private-field"
+    "-Wno-unused-template"
+    "-Wno-used-but-marked-unused"
+    "-Wno-zero-as-null-pointer-constant"
+    "-Wno-gnu-zero-variadic-macro-arguments"
+)
+
+list(APPEND ABSL_GCC_EXCEPTIONS_FLAGS
     "-fexceptions"
 )
 
-list(APPEND GCC_FLAGS
+list(APPEND ABSL_GCC_FLAGS
     "-Wall"
     "-Wextra"
     "-Wcast-qual"
@@ -24,7 +100,7 @@ list(APPEND GCC_FLAGS
     "-Wno-sign-compare"
 )
 
-list(APPEND GCC_TEST_FLAGS
+list(APPEND ABSL_GCC_TEST_FLAGS
     "-Wno-conversion-null"
     "-Wno-missing-declarations"
     "-Wno-sign-compare"
@@ -33,11 +109,11 @@ list(APPEND GCC_TEST_FLAGS
     "-Wno-unused-private-field"
 )
 
-list(APPEND LLVM_EXCEPTIONS_FLAGS
+list(APPEND ABSL_LLVM_EXCEPTIONS_FLAGS
     "-fexceptions"
 )
 
-list(APPEND LLVM_FLAGS
+list(APPEND ABSL_LLVM_FLAGS
     "-Wall"
     "-Wextra"
     "-Weverything"
@@ -85,7 +161,7 @@ list(APPEND LLVM_FLAGS
     "-Wstring-conversion"
 )
 
-list(APPEND LLVM_TEST_FLAGS
+list(APPEND ABSL_LLVM_TEST_FLAGS
     "-Wno-c99-extensions"
     "-Wno-missing-noreturn"
     "-Wno-missing-prototypes"
@@ -104,28 +180,28 @@ list(APPEND LLVM_TEST_FLAGS
     "-Wno-gnu-zero-variadic-macro-arguments"
 )
 
-list(APPEND MSVC_EXCEPTIONS_FLAGS
+list(APPEND ABSL_MSVC_EXCEPTIONS_FLAGS
     "/U_HAS_EXCEPTIONS"
     "/D_HAS_EXCEPTIONS=1"
     "/EHsc"
 )
 
-list(APPEND MSVC_FLAGS
+list(APPEND ABSL_MSVC_FLAGS
     "/W3"
+    "/DNOMINMAX"
+    "/DWIN32_LEAN_AND_MEAN"
+    "/D_CRT_SECURE_NO_WARNINGS"
+    "/D_SCL_SECURE_NO_WARNINGS"
+    "/D_ENABLE_EXTENDED_ALIGNED_STORAGE"
     "/wd4005"
     "/wd4068"
     "/wd4180"
     "/wd4244"
     "/wd4267"
     "/wd4800"
-    "/DNOMINMAX"
-    "/DWIN32_LEAN_AND_MEAN"
-    "/D_CRT_SECURE_NO_WARNINGS"
-    "/D_SCL_SECURE_NO_WARNINGS"
-    "/D_ENABLE_EXTENDED_ALIGNED_STORAGE"
 )
 
-list(APPEND MSVC_TEST_FLAGS
+list(APPEND ABSL_MSVC_TEST_FLAGS
     "/wd4018"
     "/wd4101"
     "/wd4503"