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Add linker dir to bin_search_flags for lld/gold for non-Clang compilers #571

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Add linker dir to bin_search_flags for lld/gold for non-Clang compilers #571

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70 changes: 50 additions & 20 deletions cc/private/toolchain/unix_cc_configure.bzl
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Original file line number Diff line number Diff line change
Expand Up @@ -164,7 +164,7 @@ def _is_linker_option_supported(repository_ctx, cc, force_linker_flags, option,
return result.stderr.find(pattern) == -1

def _find_linker_path(repository_ctx, cc, linker, is_clang):
"""Checks if a given linker is supported by the C compiler.
"""Return the path used by the compiler for the given linker.

Args:
repository_ctx: repository_ctx.
Expand All @@ -173,8 +173,15 @@ def _find_linker_path(repository_ctx, cc, linker, is_clang):
is_clang: whether the compiler is known to be clang

Returns:
String to put as value to -fuse-ld= flag, or None if linker couldn't be found.
String for the full path to the linker, or None if linker couldn't be found.
"""
if is_clang:
verbose = "-v"
else:
# GCC outputs the linker command with -Wl,-v. This doesn't get passed
# to the linker but collect2.
verbose = "-Wl,-v"

result = repository_ctx.execute([
cc,
str(repository_ctx.path("tools/cpp/empty.cc")),
Expand All @@ -186,24 +193,35 @@ def _find_linker_path(repository_ctx, cc, linker, is_clang):
"-Wl,--start-lib",
"-Wl,--end-lib",
"-fuse-ld=" + linker,
"-v",
verbose,
])
if result.return_code != 0:
return None

if not is_clang:
return linker

# Extract linker path from:
# /usr/bin/clang ...
# "/usr/bin/ld.lld" -pie -z ...
# We use the leading space and quoted path to find invocations.
# https://github.com/llvm/llvm-project/blob/85c78274358717e4d5d019a801decba5c1add484/clang/lib/Driver/Job.cpp#L207-L209
invocations = [line for line in result.stderr.splitlines() if line.startswith(" \"")]
if not invocations:
return linker
linker_command = invocations[-1]
return linker_command.strip().split(" ")[0].strip("\"'")
if is_clang:
# Extract linker path from:
# /usr/bin/clang ...
# "/usr/bin/ld.lld" -pie -z ...
# We use the leading space and quoted path to find invocations.
# https://github.com/llvm/llvm-project/blob/85c78274358717e4d5d019a801decba5c1add484/clang/lib/Driver/Job.cpp#L207-L209
invocations = [line for line in result.stderr.splitlines() if line.startswith(" \"")]
if not invocations:
return linker
linker_command = invocations[-1]
return linker_command.strip().split(" ")[0].strip("\"'")
else:
# Extract linker path from:
# collect2 version ...
# /path/to/ld.{linker} ...
lines = result.stderr.splitlines()
if len(lines) < 2:
return linker

linker_command = lines[1]
linker_args = linker_command.strip().split(" ")
if not linker_args:
return linker
return linker_args[0]

def _add_compiler_option_if_supported(repository_ctx, cc, option):
"""Returns `[option]` if supported, `[]` otherwise. Doesn't %-escape the option."""
Expand Down Expand Up @@ -495,13 +513,25 @@ def configure_unix_toolchain(repository_ctx, cpu_value, overridden_tools):
else:
# cc is inside the repository, don't set -B.
bin_search_flags = []
if not gold_or_lld_linker_path:

force_linker_flags = []
if gold_or_lld_linker_path:
if is_clang:
# Just pass the full path to clang via -fuse-ld=.
fuse_ld = gold_or_lld_linker_path
else:
# GCC doesn't support full paths for -fuse-ld=, only names, so
# we need to pass the directory via -B.
ld_path = repository_ctx.path(gold_or_lld_linker_path)
if ld_path.dirname != cc_path.dirname:
bin_search_flags.append("-B" + escape_string(str(ld_path.dirname)))
fuse_ld = ld_path.basename.removeprefix("ld.")

force_linker_flags.append("-fuse-ld=" + fuse_ld)
else:
ld_path = repository_ctx.path(tool_paths["ld"])
if ld_path.dirname != cc_path.dirname:
bin_search_flags.append("-B" + str(ld_path.dirname))
force_linker_flags = []
if gold_or_lld_linker_path:
force_linker_flags.append("-fuse-ld=" + gold_or_lld_linker_path)

# TODO: It's unclear why these flags aren't added on macOS.
if bin_search_flags and not darwin:
Expand Down