`include-what-you-use` diagnostics, in practice, are specific to
the environment's compiler and standard library. Update includes
to satisfy IWYU for our CI job under Debian 12.
To handle safely the values used by CMake variables and properties,
introduce the class cmProp as a replacement from the simple pointer
to std::string instance.
#pragma once is a widely supported compiler pragma, even though it is
not part of the C++ standard. Many of the issues keeping #pragma once
from being standardized (distributed filesystems, build farms, hard
links, etc.) do not apply to CMake - it is easy to build CMake on a
single machine. CMake also does not install any header files which can
be consumed by other projects (though cmCPluginAPI.h has been
deliberately omitted from this conversion in case anyone is still using
it.) Finally, #pragma once has been required to build CMake since at
least August 2017 (7f29bbe6 enabled server mode unconditionally, which
had been using #pragma once since September 2016 (b13d3e0d)). The fact
that we now require C++11 filters out old compilers, and it is unlikely
that there is a compiler which supports C++11 but does not support
#pragma once.
This option has been broken since commit b9f9915516 (cmMakefile: Remove
VarUsageStack., 2015-05-17, v3.3.0-rc1~52^2). That commit removed the
check that an initialized variable has actually been used and caused the
option to warn on every variable ever set. This was not caught by the
test suite because the test for the feature only checked that warnings
appear when needed and not that they do not appear when not needed.
The option was never very practical to use. Remove it to avoid the
runtime cost of usage tracking and checks for every variable (which we
were doing even when the option was not used).
Provide a standardized way to handle the C++ "standard" headers
customized to be used with current CMake C++ standard constraints.
Offer under directory `cm` headers which can be used as direct
replacements of the standard ones. For example:
#include <cm/string_view>
can be used safely for CMake development in place of the `<string_view>`
standard header.
Fixes: #19491
- Removes `cmDefinitions::Set` method overload that takes a `const char*`
value argument.
- Updates calls to `cmDefinitions::Set` to use the `cm::string_view` based
version instead.
Policies affecting the behavior of CMake-provided macros and functions
need to be able to get the policy setting as of the call site rather
than the definition site. Add an undocumented option to do this.
Port dependents to the new locations as needed.
Leave behind a cmState.h include in cmListFileCache to reduce noise. It
is removed in a following commit.
