When we use the -nostdlib++ flag, we don't need to explicitly link
against compiler-rt, since the compiler already links against it by
default. This simplifies the flags that we need to use when building
with Clang and GCC, and opens the door to further simplifications since
most platforms won't need to detect whether libgcc and libgcc_s are
supported anymore.
Furthermore, on platforms where -nostdlib++ is used, this patch prevents
manually linking compiler-rt *before* other system libraries. For
example, Apple platforms have several compiler-rt symbols defined in
libSystem.dylib. If we manually link against compiler-rt, we end up
overriding the default link order preferred by the compiler and
potentially using the symbols from the clang-provided libclang_rt.a
library instead of the system provided one.
Note that we don't touch how libunwind links against compiler-rt when it
builds the .so/.a because libunwind currently doesn't use -nodefaultlibs
and we want to avoid rocking the boat too much.
rdar://119506163
These have the same purposes but two different implementations.
llvm_check_compiler_linker_flag uses CMAKE_REQUIRED_FLAGS which affects
flags used both for compilation and linking which is problematic because
some flags may be link-only and trigger unused argument warning when set
during compilation. llvm_check_linker_flag does not have this issue so
we chose it as the prevailaing implementation.
Differential Revision: https://reviews.llvm.org/D143052
Fixes warnings (or errors, if someone injects -Werror in their build system,
which happens in fact with some folks vendoring LLVM too) with Clang 16:
```
+/var/tmp/portage.notmp/portage/sys-devel/llvm-15.0.4/work/llvm_build-abi_x86_64.amd64/CMakeFiles/CMakeTmp/src.c:3:9: warning: a function declaration without a prototype
is deprecated in all versions of C [-Wstrict-prototypes]
-/var/tmp/portage.notmp/portage/sys-devel/llvm-14.0.4/work/llvm_build-abi_x86_64.amd64/CMakeFiles/CMakeTmp/src.c:3:9: error: a function declaration without a prototype is
deprecated in all versions of C [-Werror,-Wstrict-prototypes]
int main() {return 0;}
^
void
```
Differential Revision: https://reviews.llvm.org/D137503
Done according to @phosek's comments in D117537, but not done then to
separate pure refactor (that) from possible behavior change (this).
Wasn't working before, but I think that was due to an issue of mismatched variable names fixed in D110005.
Reviewed By: phosek, #libunwind, #libc_abi
Differential Revision: https://reviews.llvm.org/D117833
The CMake variable LIBUNWIND_SUPPORTS_NODEFAULTLIBS_FLAG has been renamed
into C_SUPPORTS_NODEFAULTLIBS_FLAG because the last one is used in the
confix-ix.cmake file while the variable with the original name is not used
at al.
Differential Revision: https://reviews.llvm.org/D126466
This is a variant of D116689 rebased on top of the new (proposed) ABI
refactoring in D120727. It should conserve the basic properties of the
original patch by @phosek, except it also allows cleaning up the merging
of libc++abi into libc++ from the libc++ side.
Differential Revision: https://reviews.llvm.org/D125393
We add `--unwindlib=none` to `CMAKE_REQUIRED_FLAGS`
to make sure that builds with a yet-incomplete toolchain succeed,
to avoid linker failures about missing unwindlib.
When this option is added to `CMAKE_REQUIRED_FLAGS`, it gets added to
both compile and link commands in CMake compile tests. If
`--unwindlib=none` is included in compilation commands, it causes
warnings about unused arguments, as the flag only is relevant for
linking.
Due to the warnings in CMake tests, the later CMake test for the
`-Werror` option failed (as the tested `-Werror` option caused the
preexisting warning due to unused `--unwindlib=none` to become a
hard error). Therefore, most CI configurations that build with
`LIBCXX_ENABLE_WERROR` didn't actually end up enabling `-Werror`
after all.
When looking at the CI build log of recent CI builds, they do
end up printing:
-- Performing Test LIBCXX_SUPPORTS_WERROR_FLAG
-- Performing Test LIBCXX_SUPPORTS_WERROR_FLAG - Failed
-- Performing Test LIBCXX_SUPPORTS_WX_FLAG
-- Performing Test LIBCXX_SUPPORTS_WX_FLAG - Failed
Thus while the configurations are meant to error out on warnings,
they actually haven't done that, due to the interaction of these
options.
To fix this, remove the individual cases of adding `--unwindlib=none`
into `CMAKE_REQUIRED_FLAGS` in libcxx and libunwind.
`runtimes/CMakeLists.txt` still adds `--unwindlib=none` if needed, but
not otherwise. (The same issue with enabling `-Werror` does remain
if `--unwindlib=none` strictly is needed though - that can be fixed
separately afterwards.)
These individual cases in libunwind and libcxx were added while
standalone builds of the runtimes still were supported - but no longer
are necessary now.
Differential Revision: https://reviews.llvm.org/D124375
Avoid repeating CMake checks across runtimes by unifying names of
variables used for results to leverage CMake caching.
Differential Revision: https://reviews.llvm.org/D110005
We previously had a few varied definitions of this floating around.
I had tried to make the one installed with LLVM handle all the cases, and then made the others use it, but this ran into issues with `HandleOutOfTreeLLVM` not working for compiler-rt, and also `CMAKE_EXE_LINKER_FLAGS` not working right without `CMP0056` set to the new behavior.
My compromise solution is this:
- No not completely deduplicate: the runtime libs will instead use a version that still exists as part of the internal and not installed common shared CMake utilities. This avoids `HandleOutOfTreeLLVM` or a workaround for compiler-rt.
- Continue to use `CMAKE_REQUIRED_FLAGS`, which effects compilation and linking. Maybe this is unnecessary, but it's safer to leave that as a future change. Also means we can avoid `CMP0056` for now, to try out later, which is good incrementality too.
- Call it `llvm_check_compiler_linker_flag` since it, in fact is about both per its implementation (before and after this patch), so there is no name collision.
In the future, we might still enable CMP0056 and make compiler-rt work with HandleOutOfTreeLLVM, which case we delete `llvm_check_compiler_flag` and go back to the old way (as these are, in fact, linking related flags), but that I leave for someone else as future work.
The original issue was reported to me in https://reviews.llvm.org/D116521#3248117 as
D116521 made clang and LLVM use the common cmake utils.
Reviewed By: sebastian-ne, phosek, #libunwind, #libc, #libc_abi, ldionne
Differential Revision: https://reviews.llvm.org/D117537
We previously had a few varied definitions of this floating around. I made the one installed with LLVM handle all the cases, and then made the others use it.
This issue was reported to me in https://reviews.llvm.org/D116521#3248117 as
D116521 made clang and llvm use the common cmake utils.
Reviewed By: sebastian-ne, phosek, #libunwind, #libc, #libc_abi, ldionne
Differential Revision: https://reviews.llvm.org/D117537
When building libcxx, libcxxabi, and libunwind the build environment may
specify any number of sanitizers. For some build feature tests these
sanitizers must be disabled to prevent spurious linking errors. With
-fsanitize= this is straight forward with -fno-sanitize=all. With
-fsanitize-coverage= there is no -fno-sanitize-coverage=all, but there
is the equivalent undocumented but tested -fsanitize-coverage=0.
The current build rules fail to disable 'trace-pc-guard'. By disabling
all sanitize-coverage flags, including 'trace-pc-guard', possible
spurious linker errors are prevented. In particular, this allows libcxx,
libcxxabi, and libunwind to be built with HonggFuzz.
CMAKE_REQUIRED_FLAGS is extra compile flags when running CMake build
configuration steps (like check_cxx_compiler_flag). It does not affect
the compile flags for the actual build of the project (unless of course
these flags change whether or not a given source compiles and links or
not). So libcxx, libcxxabi, and libunwind will still be built with any
specified sanitize-coverage as before. The build configuration steps
(which are mostly checking to see if certain compiler flags are
available) will not try to compile and link "int main() { return 0;}"
(or other specified source) with sanitize-coverage (which can fail to
link at this stage in building, since the final compile flags required
are yet to be determined).
The change to LIBFUZZER_CFLAGS was done to keep it consistent with the
obvious intention of disabling all sanitize-coverage. This appears to
be intentional, preventing the fuzzer driver itself from showing up in
any coverage calculations.
Reviewed By: #libunwind, #libc, #libc_abi, ldionne, phosek
Differential Revision: https://reviews.llvm.org/D116050
If Clang is set up to link directly against libunwind (via the
--unwindlib option, or the corresponding builtin default option),
configuring libunwind will fail while bootstrapping (before the
initial libunwind is built), because every cmake test will
fail due to -lunwind not being found, and linking the shared library
will fail similarly.
Check if --unwindlib=none is supported, and add it in that case.
Using check_c_compiler_flag on its own doesn't work, because that only
adds the tested flag to the compilation command, and if -lunwind is
missing, the linking step would still fail - instead try adding it
to CMAKE_REQUIRED_FLAGS and restore the variable if it doesn't work.
This avoids having to pass --unwindlib=none while building libunwind.
Differential Revision: https://reviews.llvm.org/D112126
There's a lot of duplicated calls to find various compiler-rt libraries
from build of runtime libraries like libunwind, libc++, libc++abi and
compiler-rt. The compiler-rt helper module already implemented caching
for results avoid repeated Clang invocations.
This change moves the compiler-rt implementation into a shared location
and reuses it from other runtimes to reduce duplication and speed up
the build.
Differential Revision: https://reviews.llvm.org/D88458
There's a lot of duplicated calls to find various compiler-rt libraries
from build of runtime libraries like libunwind, libc++, libc++abi and
compiler-rt. The compiler-rt helper module already implemented caching
for results avoid repeated Clang invocations.
This change moves the compiler-rt implementation into a shared location
and reuses it from other runtimes to reduce duplication and speed up
the build.
Differential Revision: https://reviews.llvm.org/D88458
When a target triple is specified in CMake via XXX_TARGET_TRIPLE, we tried
passing the --target=<...> flag to the compiler. However, not all compilers
support that flag (e.g. GCC, which is not a cross-compiler). As a result,
setting e.g. LIBCXX_TARGET_TRIPLE=<host-triple> would end up trying to
pass --target=<host-triple> to GCC, which breaks everything because the
flag isn't even supported.
This commit only adds `--target=<...>` & friends to the flags if it is
supported by the compiler.
One could argue that it's confusing to pass LIBCXX_TARGET_TRIPLE=<...>
and have it be ignored. That's correct, and one possibility would be
to assert that the requested triple is the same as the host triple when
we know the compiler is unable to cross-compile. However, note that this
is a pre-existing issue (setting the TARGET_TRIPLE variable never had an
influence on the flags passed to the compiler), and also fixing that is
starting to look like reimplementing a lot of CMake logic that is already
handled with CMAKE_CXX_COMPILER_TARGET.
Differential Revision: https://reviews.llvm.org/D106082
Let's use -nostdlib++ rather than -nodefaultlibs when building libc++/libc++abi/libunwind libraries. The default is -nostdlib++ if supported by a build compiler like it is the case with clang, otherwise -nodefaultlibs is used as before.
This change is needed to avoid additional changes at the link step and not to increase the maintenance costs. If clang with -nodefaultlibs is used all the libraries which are removed but required would have to be manually added in. This set of libraries are unique and will send out.
The propose change will allow to make the link step simple for other platforms as well.
Reviewed By: #libc, #libc_abi, ldionne
Differential Revision: https://reviews.llvm.org/D95875
Android doesn't have a libgcc_s and uses libgcc instead, so adjust the
build accordingly. This matches compiler-rt's build setup. libc++abi and
libunwind were already checking for libgcc but in a different context.
This change makes them search only for libgcc on Android now, but the
code to link against libgcc if it were present was already there.
Reviewed By: #libc, #libc_abi, #libunwind, rprichard, srhines
Differential Revision: https://reviews.llvm.org/D78787
Summary:
Relands https://reviews.llvm.org/D70815.
The original commit set `CMAKE_TRY_COMPILE_TARGET_TYPE` to
`STATIC_LIBRARY` globally in libunwind/CMakeLists.txt, which effectively
disabled the linking step in CMake checks.
This broke some builds (see 938c70b86c).
Here we set CMAKE_TRY_COMPILE_TARGET_TYPE to
STATIC_LIBRARY only when checking for presence of the `-funwind-tables`
flag, and then set it back to the original value so it doesn't affect
other checks.
Reviewers: mstorsjo, jfb
Subscribers: mgorny, christof, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D71117
This reverts commit b3fdf33ba6.
This change broke building libunwind for Windows/MinGW, and broke
on aspect of the CMake tests in libunwind in general.
After set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY), CMake
skips the linking step in tests, but cmake/config-ix.cmake also
does a few checks for functions in libraries (looking for whether
-lc provides fopen and whether -ldl provides dladdr).
As CMake only tests building a static library, these tests
incorrectly succeed and CMake concludes "Looking for fopen in c -
found" and "Looking for dladdr in dl - found", while building
then fails at the end with errors about unable to find -lc and -ldl.
Summary:
Or, rather, don't accidentally forget to pass it.
This is aimed to solve the problem discussed in [this thread](http://lists.llvm.org/pipermail/llvm-dev/2019-November/136890.html), and to fix [a year-old bug](https://bugs.llvm.org/show_bug.cgi?id=38468).
TL;DR: when building libunwind for ARM Linux, we **need** libunwind to be built with the `-funwind-tables` flag, because, well ARM EHABI needs unwind info produced by this flag. Without the flag all the procedures in libunwind are marked `.cantunwind`, which causes all sorts of bad things. From `_Unwind_Backtrace` not working, to C++ exceptions not being caught (which is the aforementioned bug is about).
Previously, this flag was not added because the CMake check `add_compile_flags_if_supported(-funwind-tables)` produced a false negative. Why? With this flag, the compiler generates calls to the `__aeabi_unwind_cpp_pr0` symbol, which is defined in libunwind itself and obviously is not available at configure time, before libunwind is built. This led to failure at link time during the CMake check. We handle this by disabling the linker for CMake checks in linbunwind.
Also, this patch introduces a lit feature `libunwind-arm-ehabi`, which is used to mark the `signal_frame.pass.cpp` test as unsupported (as was advised by @miyuki in D70397).
Reviewers: peter.smith, phosek, EricWF, compnerd, jroelofs, saugustine, miyuki, jfb
Subscribers: mgorny, kristof.beyls, christof, libcxx-commits, miyuki
Tags: #libc
Differential Revision: https://reviews.llvm.org/D70815
libunwind was using its own set of macros/functions for flag checking
which was similar but different from libc++ and libc++abi. This made
it difficult to replicate the same checks across projects, in fact
there were some checks that appear to have been copy & pasted from
another project and that were broken in the standalone libunwind build.
This change refactors flag checks to match libc++ and libc++abi using
a copy of HandleLibunwindFlags.cmake which is derived from the versions
used by the other projects. This also paves a road to deduplicating and
unifying HandleLibunwindFlags.cmake, HandleLibcxxabiFlags.cmake and
HandleLibcxxFlags.cmake post monorepo switch.
Differential Revision: https://reviews.llvm.org/D68855
llvm-svn: 374606
This fixes the issue introduced by r362048 where we always use
pragma comment(lib, ...) for dependent libraries when the compiler
is Clang, but older Clang versions don't support this pragma so
we need to check first if it's supported before using it.
llvm-svn: 362055
The check_library_exists CMake uses a custom symbol definition. This
is a problem when checking for C library symbols because Clang
recognizes many of them as builtins, and returns the
-Wbuiltin-requires-header (or -Wincompatible-library-redeclaration)
error. When building with -Werror which is the default, this causes
the check_library_exists check fail making the build think that C
library isn't available.
To avoid this issue, we should use a symbol that isn't recognized by
Clang and wouldn't cause the same issue. __libc_start_main seems like
reasonable choice that fits the bill.
Differential Revision: https://reviews.llvm.org/D57142
llvm-svn: 352341
This is needed when cross-compiling for a different target since
CFLAGS may contain additional flags like -resource-dir which
change the location in which compiler-rt builtins are found.
Differential Revision: https://reviews.llvm.org/D54371
llvm-svn: 346820
Summary:
If `-nodefaultlibs` is given, we weren't actually linking to it. This
was true irrespective of passing `-rtlib=compiler-rt` (see previous
patch). Now we explicitly link it to handle that case.
I wonder if we should be linking these libraries only if we're using
`-nodefaultlibs`...
Reviewers: beanz
Subscribers: dberris, mgorny, christof, chrib, cfe-commits
Differential Revision: https://reviews.llvm.org/D51657
llvm-svn: 343990
Summary:
This switch only has an effect at link time. It changes the default
compiler support library to `compiler-rt`. With `-nodefaultlibs`, this
library won't get linked anyway; Clang actually warns about that.
Reviewers: mstorsjo, rnk
Subscribers: dberris, mgorny, christof, cfe-commits
Differential Revision: https://reviews.llvm.org/D51645
llvm-svn: 341404
The paths output from llvm-config --cmakedir and from clang
--print-libgcc-file-name can contain backslashes, while CMake
can't handle the paths in this form.
This matches what compiler-rt already does (since SVN r203789
and r293195).
Differential Revision: https://reviews.llvm.org/D48353
llvm-svn: 335169
Rather than hardcode the flag and check if the compiler supports it, use
the CMake property to get the right flag spelling for the compiler.
This makes it generally more portable.
llvm-svn: 314834
CMake has the problem with the single dash variant because of the
space, so use the double dash with equal sign version. The compile
flag handling had a typo which caused these flag not to be properly
include. We also don't have to pass the target triple when checking
for compiler-rt since that flag is already included in compile flags
now.
Differential Revision: https://reviews.llvm.org/D32071
llvm-svn: 300419
This is a reland of commit r299796.
Turned out that we need gcc_s or compiler-rt on ARM when checking
the support for -funwind-tables which creates a dependency on
__aeabi_unwind_cpp_pr0 symbol that's provided by the compiler
runtime.
Differential Revision: https://reviews.llvm.org/D31858
llvm-svn: 300020
Since libunwind is built with -nodefaultlibs, we should be using this
option even for CMake checks to avoid any inconsistency and also to
avoid dependency on a working C++ standard library just for the setting
up the build itself. The implementation is largely similar to the one
used by libc++.
Differential Revision: https://reviews.llvm.org/D31640
llvm-svn: 299796
The new LLVM runtimes directory requires the same conventions to be
followed across the runtime projects. These changes make libunwind
build under the runtimes subdirectory.
This patch contains the following changes:
* Rename LLVM_CONFIG to LLVM_CONFIG_PATH
* Check if compiler supports C++11 (required by libunwind)
Differential Revision: https://reviews.llvm.org/D26360
llvm-svn: 286308
This replicates most of the build infrastructure from libc++abi ported to
libunwind. This allows building libunwind without requiring libc++abi.
llvm-svn: 235795
