We do not add default warning flags on other compilers, and having
a warning flag in the default flags makes it hard for projects to
customize the warning level. They need to use string processing
to remove `/W3` from `CMAKE_{C,CXX}_FLAGS`. Therefore we should
drop it.
However, projects may be using string processing to replace `/W3`
with another flag, so we cannot simply drop it. Add a policy to
drop it in a compatible way.
Fixes: #18317
Replace our hard-coded defaults for `/MD` and `/MDd` with a first-class
abstraction to select the runtime library from an enumeration of logical
names. We've long hesitated to do this because the idea of "runtime
library selection" touches on related concepts on several platforms.
Avoid that scope creep by simply defining an abstraction that applies
only when targeting the MSVC ABI on Windows.
Removing the old default flags requires a policy because existing
projects may rely on string processing to edit them and choose a runtime
library under the old behavior. Add policy CMP0091 to provide
compatibility.
Fixes: #19108
Document these variables.
Change our convention for setting these variables from:
set(CMAKE_C_FLAGS_INIT "...")
to
string(APPEND CMAKE_C_FLAGS_INIT " ...")
so that any value previously set by a toolchain file will be used.
Automate the conversion with:
sed -i 's/set *(\(CMAKE_\(C\|CXX\|Fortran\|RC\|ASM\|${[^}]\+}\)_FLAGS\(_[^_]\+\)\?_INIT \+"\)/string(APPEND \1 /' \
Modules/Compiler/*.cmake Modules/Platform/*.cmake
and follow up with some manual fixes (e.g. to cases that already
meant to append). Also revert the automated changes to contexts
that are not protected from running multiple times.
We define `NDEBUG` without a space after the `-D` option for most
compilers. Remove the space for MSVC (and Intel Fortran) for
consistency. The MS compiler technically does not document that
the `-D` argument may be separated from its value, though every
version to date supports it.
Fix typo introduced in commit 66a08c10 (more uniform approach to enable
language, 2004-08-26). The optimization option should be /O2 for
Release configurations and /O1 for MinSizeRel.
Suggested-by: He Yuqi <yuqi.he@gmail.com>
This moves Intel compiler info on Windows into new-style modules
Platform/Windows-Intel-<lang>.cmake
using language-independent helper module
Platform/Windows-Intel.cmake
to define macros consolidating the information.
