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[cmake] Restore exception flags in llvm-config --cxxflags#176195

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nikic merged 1 commit intollvm:mainfrom
nikic:llvm-config-exceptions
Jan 16, 2026
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[cmake] Restore exception flags in llvm-config --cxxflags#176195
nikic merged 1 commit intollvm:mainfrom
nikic:llvm-config-exceptions

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@nikic nikic commented Jan 15, 2026

#173869 accidentally dropped rtti and eh flags from llvm-config --cxxflags. Then #174084 restored the rtti flags. The eh flags were not included with the rationale that they are not ABI relevant.

This PR restores the eh flags as well. While they are not strictly necessary, I believe that code that directly interfaces with LLVM almost certainly does not want to build with exceptions if LLVM is not built with exceptions. Building in the peculiar -fexceptions -fno-rtti configuration is rarely useful and likely not intended.

On MacOS, this is also relevant because it's not possible to use C++17 headers without -fno-exceptions when using older deployment targets. In that configuration, -fno-exceptions is required to interact with LLVM.

@nikic nikic requested a review from aengelke January 15, 2026 16:04
@llvmbot llvmbot added the cmake Build system in general and CMake in particular label Jan 15, 2026
@nikic nikic mentioned this pull request Jan 15, 2026
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aengelke approved these changes Jan 15, 2026
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LGTM. The whole thing is just incredibly messy and if this causes breakage, let's not try to win points for purity here.

A summary of the messiness:

  • -fno-exceptions/-fno-rtti are only exposed via llvm-config, not via CMake when linking against LLVM. CMake users have to add these manually.
  • CMake by-default adds /EHsc for MSVC (/GR was dropped with CMake 3.20, which we require).
  • MSVC warns about option mismatch, this warning can't be disabled.
  • One unittest unconditionally wants exceptions, with MSVC this forces us to do this per-target flag update and prevent us from just setting it in the global CMAKE_CXX_FLAGS.
  • Many Linux distributions build with -frtti, because some users use rtti to avoid this incompatibility.

llvm/cmake/modules/AddLLVM.cmake
endif()
elseif(MSVC)
if(MSVC)
list(APPEND LLVM_COMPILE_DEFINITIONS _HAS_EXCEPTIONS=0)
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Given that this is now the only use of LLVM_COMPILE_DEFINITIONS, just use target_compile_definitions(${name} PRIVATE _HAS_EXCEPTIONS=0) here?

@nikic nikic mentioned this pull request Jan 15, 2026
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@nikic nikic merged commit 9bbea75 into llvm:main Jan 16, 2026
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@nikic nikic deleted the llvm-config-exceptions branch January 16, 2026 08:33
@nikic nikic added this to the LLVM 22.x Release milestone Jan 16, 2026
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nikic commented Jan 16, 2026

/cherry-pick 9bbea75

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llvmbot commented Jan 16, 2026

/pull-request #176328

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llvm-ci commented Jan 16, 2026

LLVM Buildbot has detected a new failure on builder lldb-aarch64-windows running on linaro-armv8-windows-msvc-05 while building llvm at step 6 "test".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/141/builds/14517

Here is the relevant piece of the build log for the reference 
Step 6 (test) failure: build (failure)
...
UNSUPPORTED: lldb-api :: functionalities/thread/create_after_attach/TestCreateAfterAttach.py (693 of 2396)
PASS: lldb-api :: functionalities/thread/exit_during_break/TestExitDuringBreak.py (694 of 2396)
UNSUPPORTED: lldb-api :: functionalities/thread/exit_during_expression/TestExitDuringExpression.py (695 of 2396)
UNSUPPORTED: lldb-api :: functionalities/thread/exit_during_step/TestExitDuringStep.py (696 of 2396)
PASS: lldb-api :: functionalities/thread/finish-from-empty-func/TestEmptyFuncThreadStepOut.py (697 of 2396)
PASS: lldb-api :: functionalities/thread/ignore_suspended/TestIgnoreSuspendedThread.py (698 of 2396)
UNSUPPORTED: lldb-api :: functionalities/thread/create_during_step/TestCreateDuringStep.py (699 of 2396)
UNSUPPORTED: lldb-api :: functionalities/thread/main_thread_exit/TestMainThreadExit.py (700 of 2396)
UNSUPPORTED: lldb-api :: functionalities/thread/multi_break/TestMultipleBreakpoints.py (701 of 2396)
PASS: lldb-api :: functionalities/thread/num_threads/TestNumThreads.py (702 of 2396)
FAIL: lldb-api :: functionalities/thread/jump/TestThreadJump.py (703 of 2396)
******************** TEST 'lldb-api :: functionalities/thread/jump/TestThreadJump.py' FAILED ********************
Script:
--
C:/Users/tcwg/scoop/apps/python/current/python.exe C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/llvm-project/lldb\test\API\dotest.py -u CXXFLAGS -u CFLAGS --env LLVM_LIBS_DIR=C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./lib --env LLVM_INCLUDE_DIR=C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/include --env LLVM_TOOLS_DIR=C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./bin --arch aarch64 --build-dir C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/lldb-test-build.noindex --lldb-module-cache-dir C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/lldb-test-build.noindex/module-cache-lldb\lldb-api --clang-module-cache-dir C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/lldb-test-build.noindex/module-cache-clang\lldb-api --executable C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./bin/lldb.exe --compiler C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./bin/clang.exe --dsymutil C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./bin/dsymutil.exe --make C:/Users/tcwg/scoop/shims/make.exe --llvm-tools-dir C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./bin --lldb-obj-root C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/tools/lldb --lldb-libs-dir C:/Users/tcwg/llvm-worker/lldb-aarch64-windows/build/./lib --cmake-build-type Release --skip-category=watchpoint C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\llvm-project\lldb\test\API\functionalities\thread\jump -p TestThreadJump.py
--
Exit Code: 1

Command Output (stdout):
--
lldb version 23.0.0git (https://github.com/llvm/llvm-project.git revision 9bbea753a4a45f9c7c7ca9730736c7792adaacf9)
  clang revision 9bbea753a4a45f9c7c7ca9730736c7792adaacf9
  llvm revision 9bbea753a4a45f9c7c7ca9730736c7792adaacf9
Skipping the following test categories: watchpoint, libc++, libstdcxx, dwo, dsym, gmodules, debugserver, objc, fork, pexpect


--
Command Output (stderr):
--
UNSUPPORTED: LLDB (C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe-aarch64) :: test_dsym (TestThreadJump.ThreadJumpTestCase.test_dsym) (test case does not fall in any category of interest for this run) 

PASS: LLDB (C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe-aarch64) :: test_dwarf (TestThreadJump.ThreadJumpTestCase.test_dwarf)

UNSUPPORTED: LLDB (C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe-aarch64) :: test_dwo (TestThreadJump.ThreadJumpTestCase.test_dwo) (test case does not fall in any category of interest for this run) 

UNSUPPORTED: LLDB (C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe-aarch64) :: test_jump_offset_dsym (TestThreadJump.ThreadJumpTestCase.test_jump_offset_dsym) (test case does not fall in any category of interest for this run) 

FAIL: LLDB (C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe-aarch64) :: test_jump_offset_dwarf (TestThreadJump.ThreadJumpTestCase.test_jump_offset_dwarf)

UNSUPPORTED: LLDB (C:\Users\tcwg\llvm-worker\lldb-aarch64-windows\build\bin\clang.exe-aarch64) :: test_jump_offset_dwo (TestThreadJump.ThreadJumpTestCase.test_jump_offset_dwo) (test case does not fall in any category of interest for this run) 

======================================================================

FAIL: test_jump_offset_dwarf (TestThreadJump.ThreadJumpTestCase.test_jump_offset_dwarf)

   Test Thread Jump by negative or positive offset

----------------------------------------------------------------------

kkwli pushed a commit to kkwli/llvm-project that referenced this pull request Jan 16, 2026
@nikic @kkwli
[cmake] Restore exception flags in llvm-config --cxxflags (llvm#176195)
1709783 
llvm#173869 accidentally dropped
rtti and eh flags from `llvm-config --cxxflags`. Then
llvm#174084 restored the rtti
flags. The eh flags were not included with the rationale that they are
not ABI relevant.

This PR restores the eh flags as well. While they are not strictly
necessary, I believe that code that directly interfaces with LLVM almost
certainly does not want to build with exceptions if LLVM is not built
with exceptions. Building in the peculiar `-fexceptions -fno-rtti`
configuration is rarely useful and likely not intended.

On MacOS, this is also relevant because it's not possible to use C++17
headers without `-fno-exceptions` when using older deployment targets.
In that configuration, `-fno-exceptions` is required to interact with
LLVM.
Priyanshu3820 pushed a commit to Priyanshu3820/llvm-project that referenced this pull request Jan 18, 2026
@nikic @Priyanshu3820
[cmake] Restore exception flags in llvm-config --cxxflags (llvm#176195)
2fe7d94 
llvm#173869 accidentally dropped
rtti and eh flags from `llvm-config --cxxflags`. Then
llvm#174084 restored the rtti
flags. The eh flags were not included with the rationale that they are
not ABI relevant.

This PR restores the eh flags as well. While they are not strictly
necessary, I believe that code that directly interfaces with LLVM almost
certainly does not want to build with exceptions if LLVM is not built
with exceptions. Building in the peculiar `-fexceptions -fno-rtti`
configuration is rarely useful and likely not intended.

On MacOS, this is also relevant because it's not possible to use C++17
headers without `-fno-exceptions` when using older deployment targets.
In that configuration, `-fno-exceptions` is required to interact with
LLVM.
c-rhodes pushed a commit to llvmbot/llvm-project that referenced this pull request Jan 19, 2026
@nikic @c-rhodes
[cmake] Restore exception flags in llvm-config --cxxflags (llvm#176195)
2b6bdfc 
llvm#173869 accidentally dropped
rtti and eh flags from `llvm-config --cxxflags`. Then
llvm#174084 restored the rtti
flags. The eh flags were not included with the rationale that they are
not ABI relevant.

This PR restores the eh flags as well. While they are not strictly
necessary, I believe that code that directly interfaces with LLVM almost
certainly does not want to build with exceptions if LLVM is not built
with exceptions. Building in the peculiar `-fexceptions -fno-rtti`
configuration is rarely useful and likely not intended.

On MacOS, this is also relevant because it's not possible to use C++17
headers without `-fno-exceptions` when using older deployment targets.
In that configuration, `-fno-exceptions` is required to interact with
LLVM.

(cherry picked from commit 9bbea75)
BStott6 pushed a commit to BStott6/llvm-project that referenced this pull request Jan 22, 2026
@nikic @BStott6
[cmake] Restore exception flags in llvm-config --cxxflags (llvm#176195)
bc78b62 
llvm#173869 accidentally dropped
rtti and eh flags from `llvm-config --cxxflags`. Then
llvm#174084 restored the rtti
flags. The eh flags were not included with the rationale that they are
not ABI relevant.

This PR restores the eh flags as well. While they are not strictly
necessary, I believe that code that directly interfaces with LLVM almost
certainly does not want to build with exceptions if LLVM is not built
with exceptions. Building in the peculiar `-fexceptions -fno-rtti`
configuration is rarely useful and likely not intended.

On MacOS, this is also relevant because it's not possible to use C++17
headers without `-fno-exceptions` when using older deployment targets.
In that configuration, `-fno-exceptions` is required to interact with
LLVM.
rust-bors bot pushed a commit to rust-lang/rust that referenced this pull request Jan 27, 2026
@bors
Auto merge of #150722 - nikic:llvm-22, r=cuviper
917820a 
Update to LLVM 22

Scheduled release date: Feb 24
1.94 becomes stable: Mar 5

Changes:
 * Update to rc2, with one patch to work around our outdated illumos sysroot (rust-lang/llvm-project@41256ab).
 * Update the host toolchain as well, otherwise we lose cross-language LTO, in particular for jemalloc.
 * Adjust one loongarch assembly test. The split into r and s variants is based on the suggestion in #151134.

Depends on:

 * [x] #151410
 * [ ] #150756
 * [x] llvm/llvm-project#175190
 * [x] llvm/llvm-project#175912
 * [x] llvm/llvm-project#175965
 * [x] llvm/llvm-project#176195
 * [x] llvm/llvm-project#157073
 * [x] llvm/llvm-project#176421
 * [x] llvm/llvm-project#176925
 * [x] llvm/llvm-project#177187
rust-bors bot pushed a commit to rust-lang/rust that referenced this pull request Jan 28, 2026
@bors
Auto merge of #150722 - nikic:llvm-22, r=cuviper
466ea4e 
Update to LLVM 22

Scheduled release date: Feb 24
1.94 becomes stable: Mar 5

Changes:
 * Update to rc2, with one patch to work around our outdated illumos sysroot (rust-lang/llvm-project@41256ab).
 * Update the host toolchain as well, otherwise we lose cross-language LTO, in particular for jemalloc.
 * Adjust one loongarch assembly test. The split into r and s variants is based on the suggestion in #151134.

Depends on:

 * [x] #151410
 * [ ] #150756
 * [x] llvm/llvm-project#175190
 * [x] llvm/llvm-project#175912
 * [x] llvm/llvm-project#175965
 * [x] llvm/llvm-project#176195
 * [x] llvm/llvm-project#157073
 * [x] llvm/llvm-project#176421
 * [x] llvm/llvm-project#176925
 * [x] llvm/llvm-project#177187
github-actions bot pushed a commit to rust-lang/rust-analyzer that referenced this pull request Jan 29, 2026
@bors
Auto merge of #150722 - nikic:llvm-22, r=cuviper
d9a55f4 
Update to LLVM 22

Scheduled release date: Feb 24
1.94 becomes stable: Mar 5

Changes:
 * Update to rc2, with one patch to work around our outdated illumos sysroot (rust-lang/llvm-project@41256ab).
 * Update the host toolchain as well, otherwise we lose cross-language LTO, in particular for jemalloc.
 * Adjust one loongarch assembly test. The split into r and s variants is based on the suggestion in rust-lang/rust#151134.

Depends on:

 * [x] rust-lang/rust#151410
 * [ ] rust-lang/rust#150756
 * [x] llvm/llvm-project#175190
 * [x] llvm/llvm-project#175912
 * [x] llvm/llvm-project#175965
 * [x] llvm/llvm-project#176195
 * [x] llvm/llvm-project#157073
 * [x] llvm/llvm-project#176421
 * [x] llvm/llvm-project#176925
 * [x] llvm/llvm-project#177187
github-actions bot pushed a commit to rust-lang/rustc-dev-guide that referenced this pull request Jan 29, 2026
@bors
Auto merge of #150722 - nikic:llvm-22, r=cuviper
8355195 
Update to LLVM 22

Scheduled release date: Feb 24
1.94 becomes stable: Mar 5

Changes:
 * Update to rc2, with one patch to work around our outdated illumos sysroot (rust-lang/llvm-project@41256ab).
 * Update the host toolchain as well, otherwise we lose cross-language LTO, in particular for jemalloc.
 * Adjust one loongarch assembly test. The split into r and s variants is based on the suggestion in rust-lang/rust#151134.

Depends on:

 * [x] rust-lang/rust#151410
 * [ ] rust-lang/rust#150756
 * [x] llvm/llvm-project#175190
 * [x] llvm/llvm-project#175912
 * [x] llvm/llvm-project#175965
 * [x] llvm/llvm-project#176195
 * [x] llvm/llvm-project#157073
 * [x] llvm/llvm-project#176421
 * [x] llvm/llvm-project#176925
 * [x] llvm/llvm-project#177187
github-actions bot pushed a commit to rust-lang/miri that referenced this pull request Jan 30, 2026
@bors
Auto merge of #150722 - nikic:llvm-22, r=cuviper
1a90b7a 
Update to LLVM 22

Scheduled release date: Feb 24
1.94 becomes stable: Mar 5

Changes:
 * Update to rc2, with one patch to work around our outdated illumos sysroot (rust-lang/llvm-project@41256ab).
 * Update the host toolchain as well, otherwise we lose cross-language LTO, in particular for jemalloc.
 * Adjust one loongarch assembly test. The split into r and s variants is based on the suggestion in rust-lang/rust#151134.

Depends on:

 * [x] rust-lang/rust#151410
 * [ ] rust-lang/rust#150756
 * [x] llvm/llvm-project#175190
 * [x] llvm/llvm-project#175912
 * [x] llvm/llvm-project#175965
 * [x] llvm/llvm-project#176195
 * [x] llvm/llvm-project#157073
 * [x] llvm/llvm-project#176421
 * [x] llvm/llvm-project#176925
 * [x] llvm/llvm-project#177187
github-actions bot pushed a commit to rust-lang/stdarch that referenced this pull request Feb 5, 2026
@bors
Auto merge of #150722 - nikic:llvm-22, r=cuviper
89018e5 
Update to LLVM 22

Scheduled release date: Feb 24
1.94 becomes stable: Mar 5

Changes:
 * Update to rc2, with one patch to work around our outdated illumos sysroot (rust-lang/llvm-project@41256ab).
 * Update the host toolchain as well, otherwise we lose cross-language LTO, in particular for jemalloc.
 * Adjust one loongarch assembly test. The split into r and s variants is based on the suggestion in rust-lang/rust#151134.

Depends on:

 * [x] rust-lang/rust#151410
 * [ ] rust-lang/rust#150756
 * [x] llvm/llvm-project#175190
 * [x] llvm/llvm-project#175912
 * [x] llvm/llvm-project#175965
 * [x] llvm/llvm-project#176195
 * [x] llvm/llvm-project#157073
 * [x] llvm/llvm-project#176421
 * [x] llvm/llvm-project#176925
 * [x] llvm/llvm-project#177187
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