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Ensure lld is used for external cmake with clang #44075

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Ensure lld is used for external cmake with clang #44075

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20 changes: 18 additions & 2 deletions bazel/envoy_build_system.bzl
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Original file line number Diff line number Diff line change
Expand Up @@ -127,18 +127,34 @@ def envoy_cmake(
generate_args = ["-GNinja"],
targets = ["", "install"],
**kwargs):
# On clang builds, point cmake at the LLVM toolchain's lld instead of the
# system linker (/bin/ld). rules_foreign_cc runs cmake with
# generate_crosstool_file=False by default, so it only exports CC/CXX and
# never passes -fuse-ld=lld to cmake's configure step. Without this,
# cmake falls back to the host /bin/ld, which can be a wrong-glibc-version
# bfd linker or may not exist at all (e.g. Arch Linux). The LLVM toolchain
# always ships ld.lld alongside clang, so -fuse-ld=lld is always safe here.
_lld_linker_entries = select({
"@envoy//bazel:clang_build": {
"CMAKE_EXE_LINKER_FLAGS": "-fuse-ld=lld",
"CMAKE_SHARED_LINKER_FLAGS": "-fuse-ld=lld",
"CMAKE_MODULE_LINKER_FLAGS": "-fuse-ld=lld",
},
"//conditions:default": {},
})

# If cache_entries is a dict, merge defaults and wrap for debug builds.
# If it's a select(), pass it through directly.
if hasattr(cache_entries, "update"):
cache_entries.update(default_cache_entries)
cache_entries_debug = dict(cache_entries)
cache_entries_debug.update(debug_cache_entries)
final_cache_entries = select({
final_cache_entries = _lld_linker_entries | select({
"@envoy//bazel:dbg_build": cache_entries_debug,
"//conditions:default": cache_entries,
})
else:
final_cache_entries = cache_entries
final_cache_entries = _lld_linker_entries | cache_entries

pf = ""
if copy_pdb:
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