There are two issues:
1. has_header() wants just the header name without surrounding <>
or similar; it fails otherwise.
2. has_header() returns a tuple of two bools, where the first element
determines whether or not the header has been found. So use
that element specifically, otherwise the tuple will always evaluate
to true because it is not empty.
Fixes: 675b47b069 ("compilers: cpp: improve libc++ vs libstdc++ detection (again)")
Now that we have access to Environment in get_assert_args, we can check what
the actual C++ stdlib provider is and only set relevant macros rather than
all possibly-relevant ones based on the compiler.
Also, while we're here, now that's sorted, wire up the GCC experimental
libc++ support in the macro emission given it doesn't uglify anything for
libstdc++ users now.
Bug: https://github.com/mesonbuild/meson/issues/12962
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Eli Schwartz <eschwartz93@gmail.com>
We're going to use it in some more places in a minute (for controlling assertions).
Bug: https://github.com/mesonbuild/meson/issues/12962
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Eli Schwartz <eschwartz93@gmail.com>
We'll need it in a moment for get_base_compile_args -> get_assert_args.
Bug: https://github.com/mesonbuild/meson/issues/12962
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Eli Schwartz <eschwartz93@gmail.com>
Followup to 90098473d5.
If the compiler already has one of these assertion macros [0] set, then don't
interfere.
e.g. a Linux distribution might be setting a stricter default than usual. This
is a pitfall many fell into with _FORTIFY_SOURCE and it's why AX_ADD_FORTIFY_SOURCE [1]
was contributed to autoconf-archive.
[0] _GLIBCXX_ASSERTIONS, _LIBCPP_HARDENING_MODE, or _LIBCPP_ENABLE_ASSERTIONS.
[1] https://www.gnu.org/software/autoconf-archive/ax_add_fortify_source.html
Bug: https://github.com/mesonbuild/meson/issues/12962
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Eli Schwartz <eschwartz93@gmail.com>
Followup to 90098473d5.
I changed my mind on this a few times. libcxx's documentation describes [0]
the hardening modes as:
"""
1) Unchecked mode/none, which disables all hardening checks.
2) Fast mode, which contains a set of security-critical checks that can be done
with relatively little overhead in constant time and are intended to be used
in production. We recommend most projects adopt this.
3) Extensive mode, which contains all the checks from fast mode and some additional
checks for undefined behavior that incur relatively little overhead but aren’t
security-critical. Production builds requiring a broader set of checks than fast
mode should consider enabling extensive mode. The additional rigour impacts performance
more than fast mode: we recommend benchmarking to determine if that is acceptable
for your program.
4) Debug mode, which enables all the available checks in the library, including
internal assertions, some of which might be very expensive. This mode is
intended to be used for testing, not in production.
"""
We chose 3) before because it felt like a better fit for what we're trying
to do and the most equivalent option to libstdc++'s _GLIBCXX_ASSERTIONS, but on
reflection, maybe we're better off picking a default with less overhead and
more importantly guarantees constant time checks.
[0] https://libcxx.llvm.org/Hardening.html#using-hardening-modes
Bug: https://github.com/mesonbuild/meson/issues/12962
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Eli Schwartz <eschwartz93@gmail.com>
By adding the option name to UserOption object, it is now possible to
display the name of the affected option when the given option value is
not valid.
Fixes#12635
Places where compiler needs it already have access to Environment object
and can use it directly.
This fixes mypy complaining that not all compilers have self.exe_wrapper
in run() method that got moved to base class.
The previous approach wasn't great because you couldn't control what the
detected C++ stdlib impl was. We just had a preference list we tweaked the
searched order for per OS. That doesn't work great for e.g. Gentoo with libc++
or Gentoo Prefix on macOS where we might be using libstdc++ even though the host
is libc++.
Jonathan Wakely, the libstdc++ maintainer, gave a helpful answer on how
to best detect libc++ vs libstdc++ via macros on SO [0]. Implement it.
TL;DR: Use <version> from C++20 if we can, use <ciso646> otherwise. Check for
_LIBCPP_VERSION as libstdc++ doesn't always define a macro.
[0] https://stackoverflow.com/a/31658120
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Eli Schwartz <eschwartz93@gmail.com>
For Clang, we now pass -D_GLIBCXX_DEBUG=1 if debugstl is enabled, and
we also pass -D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_DEBUG.
Per https://discourse.llvm.org/t/building-a-program-with-d-libcpp-debug-1-against-a-libc-that-is-not-itself-built-with-that-define/59176/3,
we can't use _LIBCPP_DEBUG for older Clang versions as it's unreliable unless
libc++ was built with it.
We choose MODE_DEBUG for stldebug while building with assertions will do
MODE_EXTENSIVE.
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Eli Schwartz <eschwartz93@gmail.com>
None of the options set here affect ABI and are intended for detecting constraint
violations.
For GCC, we simply need to set -D_GLIBCXX_ASSERTIONS.
For Clang, the situation is far more complicated:
* LLVM 18 uses a 'hardened mode' (https://libcxx.llvm.org/Hardening.html).
There are several levels of severity available here. I've chosen
_LIBCPP_HARDENING_MODE_EXTENSIVE as the strongest-but-one. The strongest
one (_DEBUG) doesn't affect ABI still but is reserved for stldebug.
* LLVM 15 uses a similar approach to libstdc++ called '_LIBCPP_ENABLE_ASSERTIONS'
Note that LLVM 17 while in development had fully deprecated _LIBCPP_ENABLE_ASSERTIONS
in favour of hardened, but changed its mind last-minute: https://discourse.llvm.org/t/rfc-hardening-in-libc/73925/4.
Signed-off-by: Sam James <sam@gentoo.org>
Signed-off-by: Eli Schwartz <eschwartz93@gmail.com>
This replaces all of the Apache blurbs at the start of each file with an
`# SPDX-License-Identifier: Apache-2.0` string. It also fixes existing
uses to be consistent in capitalization, and to be placed above any
copyright notices.
This removes nearly 3000 lines of boilerplate from the project (only
python files), which no developer cares to look at.
SPDX is in common use, particularly in the Linux kernel, and is the
recommended format for Meson's own `project(license: )` field
The <lang>_stdlib can be used in cross files to use a custom standard library
for a given language.
When cpp_stdlib is used in a cross file, meson passes
* -nostdinc++ to the compiler
* -nostlib to the linker
According to [1] (gcc) and [2] (clang), we should pass -nostlib++ to the linker
when we don't want to link to the standard C++ library.
Currently, we pass -nostlib.
Fix this by implementing a C++ specific get_no_stdlib_link_args() function.
[1] https://gcc.gnu.org/onlinedocs/gcc/Link-Options.html#index-nostdlib_002b_002b
[2] https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-nostdlib
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
c++26 support was added in #11986, but regressed in #10332 because
the versions now get checked against the global _ALL_STDS list, and
c++26 was missing there.
Fix by adding c++26 to _ALL_STDS
Projects that prefer GNU C but can fallback to ISO C can now set for
example `default_options: 'c_std=gnu11,c11'` and it will use gnu11 when
available, fallback to c11 otherwise. It is an error only if none of the
values are supported by the current compiler.
This allows to deprecate gnuXX values from MSVC compiler, that means
that `default_options: 'c_std=gnu11'` will now print warning with MSVC
but still fallback to 'c11' value. No warning is printed if at least one
of the values is valid, i.e. `default_options: 'c_std=gnu11,c11'`.
In the future that deprecation warning will become an hard error because
`c_std=gnu11` should mean GNU is required, for projects that cannot be
built with MSVC for example.
GCC 12.3 and Clang 16 support -std flags for c++23/c++2b. The unreleased
GCC 14 and Clang 17 will support -std flags for c++26/c++2c.
Signed-off-by: Steven Noonan <steven@uplinklabs.net>
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
The c++23 mappings apply to current production compilers (GCC, Clang).
None of the production c++ compilers support c++26 flags yet, but this
mapping will be ready once they do.
Signed-off-by: Steven Noonan <steven@uplinklabs.net>
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Instead of hardcoding any values, hardcode what we think the most likely
implementation is, and check that first. It was pointed out that while
for example, Apple only provides libc++ and supports that for xcode, a
user could install a custom environment (such as homebrew) which uses
it's own copy of libstdc++, and we need to account for that. This means
that a library search will be done, but only once and the result will be
cached, on all systems.
Currently, we hardcode libc++ for MacOS (and derivatives), and libstdc++
for all other cases. Clang had some hackery to make this work in many
cases. However, this doesn't always work, namely if you try to to use
Rust as the linker when libc++ is required.
This implementation does, as an optimization, provide a hardcoded list
of OSes we know always use libc++, and otherwise will attempt to detect
it. As a second optimization, the detected values are cached, so the
lookup is only done once
fixes: #11921
This saves on a 1500-line import at startup and may be skipped entirely
if no compiled languages are used. In exchange, we move the
implementation to a new file that is imported instead.
Followup to commit ab20eb5bbc.
There are lots of warnings that become fatal, that are simply unfixable
by the end user. Things like using old versions of software (because
they're using some kind of LTS release), warnings about compilers not
supporting certain kinds of checks, or standards being upgraded due to
skipped implementations (MSVC has c++98 and c++14, but not c++11). None
of these should be fatal, they're informative, and too important to
reduce to notices, but not important enough to stop meson if they're
printed.
Adds a new maximum warning level that is roughly equivalent to "all warnings".
This adds a way to use `/Wall` with MSVC (without the previous broken warning),
`-Weverything` with clang, and almost all general warnings in GCC with
strictness roughly equivalent to clang's `-Weverything`.
The GCC case must be implemented by meson since GCC doesn't provide a similar
option. To avoid maintenance headaches for meson, this warning level is
defined objectively: all warnings are included except those that require
specific values or are specific to particular language revisions. This warning
level is mainly intended for new code, and it is expected (nearly guaranteed)
that projects will need to add some suppressions to build cleanly with it.
More commonly, it's just a handy way to occasionally take a look at what
warnings are present with some compiler, in case anything interesting shows up
you might want to enable in general.
Since the warnings enabled at this level are inherently unstable with respect
to compiler versions, it is intended for use by developers and not to be set as
the default.
-Wnon-virtual-dtor is not what people think of as a standard warning
flag. It was previously removed from -Wall in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=16190 on the grounds that
people didn't like it and were refusing to use -Wall at all because it
forced this warning. Instead, it is enabled by -Weffc++ which is
typically not enabled and even comes with GCC documentation warnings
stating that the standard library doesn't obey it, and you might need to
`grep -v` and filter out warnings. (!!!)
It doesn't fit into the typical semantics of Meson's warning_level
option, which usually aligns with compiler standard warning levels
rather than a niche ideological warning level.
It was originally added in commit 22af56e05a,
but without any specific rationale included, and has gone unquestioned
since then -- except by the Meson users who see it, assume there is a
finely crafted design behind it, and quietly opt out by rolling their own
warning options with `add_project_arguments('-Wall', ...)`.
Furthermore a GCC component maintainer for the C++ standard library
opened a Meson bug report specially to tell us that this warning flag is
a "dumb option" and "broken by design" and "doesn't warn about the right
thing anyway", thus it should not be used. This is a reasonably
authoritative source that maybe, just maybe, this flag... is too
opinionated to force upon Meson users without recourse. It's gone beyond
opinionated and into the realm of compiler vendors seem to think that
the state of the language would be better if the flag did not exist at
all, whether default or not.
Fixes#11096
We compared a Visual Studio (the IDE) version, but we wanted a MSVC (the
compiler) version. This caused the option to be passed for a few too
many versions of MSVC, and emit a "D9002 : ignoring unknown option" on
those systems.
Compare the correct version using the version mapping from
https://walbourn.github.io/vs-2017-15-7-update/Fixes#10787
Co-authored-by: CorrodedCoder <38778644+CorrodedCoder@users.noreply.github.com>
Dylan Baker
Barnabás Pőcze
Jussi Pakkanen
Sam James
Charles Brunet
Xavier Claessens
Petr Machacek
Mattijs Korpershoek
Benjamin Redelings
Christoph Reiter
Steven Noonan
Tristan Partin
Eli Schwartz
Nomura
Luke Elliott
Kleis Auke Wolthuizen
David Robillard
Robert Cohn