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fix: standard library selection in toolchain #96

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Merged
merged 2 commits into from
Jun 22, 2023
Merged

fix: standard library selection in toolchain #96

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e2858d7
working
jungleraptor Jun 20, 2023
7e30f46
clean up
jungleraptor Jun 21, 2023
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12 changes: 12 additions & 0 deletions cc/BUILD.bazel
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Original file line number Diff line number Diff line change
Expand Up @@ -106,3 +106,15 @@ config_setting(
flag_values = {":enable_sysroot": "true"},
visibility = ["//visibility:public"],
)

bool_flag(
name = "use_libstdcpp",
build_setting_default = False,
visibility = ["//visibility:public"],
)

config_setting(
name = "_use_libstdcpp",
flag_values = {":use_libstdcpp": "true"},
visibility = ["//visibility:public"],
)
41 changes: 23 additions & 18 deletions cc/toolchains/llvm/cc_toolchain_config.bzl
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Expand Up @@ -35,7 +35,7 @@ def cc_toolchain_config(
if not is_target_triplet(target_system_name):
fail(target_system_name + " is not a target tripplet")

use_libstdcpp = builtin_sysroot != None and not is_darwin
is_cross_compile = host_system_name != target_system_name

# Default compiler flags:
compile_flags = [
Expand Down Expand Up @@ -81,15 +81,22 @@ def cc_toolchain_config(
cxx_flags = [
# The whole codebase should build with c++14
"-std=c++14",
# Use bundled libc++ for hermeticity if not cross compiling
] + ["-stdlib=libstdc++"] if use_libstdcpp else ["-stdlib=libc++"]
] + select({
"//cc:_use_libstdcpp": ["-stdlib=libstdc++"],
"//cc:_enable_sysroot": ["-stdlib=libstdc++"],
"//conditions:default": ["-stdlib=libstdc++"] if is_cross_compile else ["-stdlib=libc++"],
})

link_flags = [
"--target=" + target_system_name,
"-lm",
"-no-canonical-prefixes",
]

link_libcpp = []

link_libstdcpp = ["-l:libstdc++.a"]

# Similar to link_flags, but placed later in the command line such that
# unused symbols are not stripped.
link_libs = []
Expand Down Expand Up @@ -124,20 +131,14 @@ def cc_toolchain_config(
"-ldl",
])

if use_libstdcpp:
link_flags.extend([
# Use libstdc++ from the sysroot when cross compiling
"-l:libstdc++.a",
])
else:
link_flags.extend([
# Below this line, assumes libc++ & lld
"-l:libc++.a",
"-l:libc++abi.a",
"-l:libunwind.a",
# Compiler runtime features.
"-rtlib=compiler-rt",
])
link_libcpp.extend([
# Below this line, assumes libc++ & lld
"-l:libc++.a",
"-l:libc++abi.a",
"-l:libunwind.a",
# Compiler runtime features.
"-rtlib=compiler-rt",
])
else:
# The comments below were copied directly from:
# https://github.com/grailbio/bazel-toolchain/blob/795d76fd03e0b17c0961f0981a8512a00cba4fa2/toolchain/cc_toolchain_config.bzl#L202
Expand Down Expand Up @@ -212,7 +213,11 @@ def cc_toolchain_config(
dbg_compile_flags = dbg_compile_flags,
opt_compile_flags = opt_compile_flags,
cxx_flags = cxx_flags,
link_flags = link_flags,
link_flags = link_flags + select({
"//cc:_use_libstdcpp": link_libstdcpp,
"//cc:_enable_sysroot": link_libstdcpp,
"//conditions:default": link_libstdcpp if is_cross_compile else link_libcpp,
}),
link_libs = link_libs,
opt_link_flags = opt_link_flags,
unfiltered_compile_flags = unfiltered_compile_flags,
Expand Down