[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, 18 insertions, 18 deletions

diff --git a/absl/copts/configure_copts.bzl b/absl/copts/configure_copts.bzl
index 57cd3f62..1655addd 100644
--- a/absl/copts/configure_copts.bzl
+++ b/absl/copts/configure_copts.bzl
@@ -6,35 +6,35 @@ change Abseil copts, edit absl/copts/copts.py
 
 load(
     "//absl:copts/GENERATED_copts.bzl",
-    "GCC_EXCEPTIONS_FLAGS",
-    "GCC_FLAGS",
-    "GCC_TEST_FLAGS",
-    "LLVM_EXCEPTIONS_FLAGS",
-    "LLVM_FLAGS",
-    "LLVM_TEST_FLAGS",
-    "MSVC_EXCEPTIONS_FLAGS",
-    "MSVC_FLAGS",
-    "MSVC_TEST_FLAGS",
+    "ABSL_GCC_EXCEPTIONS_FLAGS",
+    "ABSL_GCC_FLAGS",
+    "ABSL_GCC_TEST_FLAGS",
+    "ABSL_LLVM_EXCEPTIONS_FLAGS",
+    "ABSL_LLVM_FLAGS",
+    "ABSL_LLVM_TEST_FLAGS",
+    "ABSL_MSVC_EXCEPTIONS_FLAGS",
+    "ABSL_MSVC_FLAGS",
+    "ABSL_MSVC_TEST_FLAGS",
 )
 
 ABSL_DEFAULT_COPTS = select({
-    "//absl:windows": MSVC_FLAGS,
-    "//absl:llvm_compiler": LLVM_FLAGS,
-    "//conditions:default": GCC_FLAGS,
+    "//absl:windows": ABSL_MSVC_FLAGS,
+    "//absl:llvm_compiler": ABSL_LLVM_FLAGS,
+    "//conditions:default": ABSL_GCC_FLAGS,
 })
 
 # in absence of modules (--compiler=gcc or -c opt), cc_tests leak their copts
 # to their (included header) dependencies and fail to build outside absl
 ABSL_TEST_COPTS = ABSL_DEFAULT_COPTS + select({
-    "//absl:windows": MSVC_TEST_FLAGS,
-    "//absl:llvm_compiler": LLVM_TEST_FLAGS,
-    "//conditions:default": GCC_TEST_FLAGS,
+    "//absl:windows": ABSL_MSVC_TEST_FLAGS,
+    "//absl:llvm_compiler": ABSL_LLVM_TEST_FLAGS,
+    "//conditions:default": ABSL_GCC_TEST_FLAGS,
 })
 
 ABSL_EXCEPTIONS_FLAG = select({
-    "//absl:windows": MSVC_EXCEPTIONS_FLAGS,
-    "//absl:llvm_compiler": LLVM_EXCEPTIONS_FLAGS,
-    "//conditions:default": GCC_EXCEPTIONS_FLAGS,
+    "//absl:windows": ABSL_MSVC_EXCEPTIONS_FLAGS,
+    "//absl:llvm_compiler": ABSL_LLVM_EXCEPTIONS_FLAGS,
+    "//conditions:default": ABSL_GCC_EXCEPTIONS_FLAGS,
 })
 
 ABSL_EXCEPTIONS_FLAG_LINKOPTS = select({