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Force __cxa_can_catch in LTO with exceptions #27578

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Force __cxa_can_catch in LTO with exceptions #27578

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21 changes: 13 additions & 8 deletions tools/building.py
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Original file line number Diff line number Diff line change
Expand Up @@ -195,14 +195,19 @@ def lld_flags_for_executable(external_symbols):
not settings.ASYNCIFY):
cmd.append('--strip-debug')

if cmdline.options.lto and not settings.EXIT_RUNTIME:
# The WebAssembly backend can generate new references to `__cxa_atexit` at
# LTO time. This `-u` flag forces the `__cxa_atexit` symbol to be
# included at LTO time. For other such symbols we exclude them from LTO
# and always build them as normal object files, but that would inhibit the
# LowerGlobalDtors optimization which allows destructors to be completely
# removed when __cxa_atexit is a no-op.
cmd.append('-u__cxa_atexit')
if cmdline.options.lto:
if not settings.EXIT_RUNTIME:
# The WebAssembly backend can generate new references to `__cxa_atexit` at
# LTO time. This `-u` flag forces the `__cxa_atexit` symbol to be
# included at LTO time. For other such symbols we exclude them from LTO
# and always build them as normal object files, but that would inhibit the
# LowerGlobalDtors optimization which allows destructors to be completely
# removed when __cxa_atexit is a no-op.
cmd.append('-u__cxa_atexit')
if not settings.DISABLE_EXCEPTION_CATCHING:
# The WebAssembly backend can generate new references to `__cxa_find_matching_catch_N`
# at LTO time, which depends on `__cxa_can_catch` in libc++abi.
cmd.append('-u__cxa_can_catch')

c_exports = [e for e in settings.EXPORTED_FUNCTIONS if is_c_symbol(e)]
# Strip the leading underscores
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