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Merged
tgross35 merged 2 commits into from
Sep 6, 2026
+129 −37
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build: Assert that cfg makes sense #5491

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02a19cc
build: Assert that cfg makes sense
tgross35 Sep 5, 2026
6d3103c
util: Print the time it took to do the checks
tgross35 Sep 6, 2026
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160 changes: 124 additions & 36 deletions build.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -36,12 +36,12 @@ enum Cfg {

VxworksLt25_09,

/// Corresponds to `__USE_TIME_BITS64` in UAPI
/// Corresponds to `__USE_TIME_BITS64` in UAPI. Implies 32-bit Linux target.
LinuxTimeBits64,
/// Corresponds to `_FILE_OFFSET_BITS=64` in glibc
/// Corresponds to `_FILE_OFFSET_BITS=64` in glibc. Implies 32-bit GNU target.
GnuFileOffsetBits64,
/// Corresponds to `_TIME_BITS=64` in glibc. Also used in x86 Windows with
/// GNU to expose a 64-bit `time_t`.
/// Corresponds to `_TIME_BITS=64` in glibc. Also used in x86 Windows with GNU
/// to expose a 64-bit `time_t`. Implies 32-bit GNU target and 64-bit `off_t`.

@dybucc dybucc Sep 6, 2026

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I don't think it's right to say that it implies 64-bit off_t. Windows
has no issues with off_t; It is time_t that is made 64-bits when
this cfg is issued.

GnuTimeBits64,
/// Musl 1.2+. Implies `target_env = "musl"`
MuslV1_2,
Expand Down Expand Up @@ -175,42 +175,49 @@ fn main() {
);
}

// The ABI of libc used by std is backward compatible with FreeBSD 12.
// The ABI of libc from crates.io is backward compatible with FreeBSD 12.
//
// On CI, we detect the actual FreeBSD version and match its ABI exactly,
// running tests to ensure that the ABI is correct.
// Allow overriding the default version for testing
let which_freebsd = if let Ok(version) = env::var("CARGO_CFG_LIBC_UNSTABLE_FREEBSD_VERSION") {
let vers = version.parse().unwrap();
println!("cargo:warning=setting FreeBSD version to {vers}");
vers
} else if libc_ci {
which_freebsd().unwrap_or(12)
} else {
12 // regardless of CARGO_FEATURE_RUSTC_DEP_OF_STD env var
};
if target_os == "freebsd" {
// The ABI of libc used by std is backward compatible with FreeBSD 12.
// The ABI of libc from crates.io is backward compatible with FreeBSD 12.
//
// On CI, we detect the actual FreeBSD version and match its ABI exactly,
// running tests to ensure that the ABI is correct.
// Allow overriding the default version for testing
let which_freebsd = if let Ok(version) = env::var("CARGO_CFG_LIBC_UNSTABLE_FREEBSD_VERSION")
{
let vers = version.parse().unwrap();
println!("cargo:warning=setting FreeBSD version to {vers}");
vers
} else if libc_ci {
which_freebsd().unwrap_or(12)
} else {
12 // regardless of CARGO_FEATURE_RUSTC_DEP_OF_STD env var
};

match which_freebsd {
x if x < 10 => panic!("FreeBSD older than 10 is not supported"),
10 => cfgs.push(Cfg::Freebsd10),
11 => cfgs.push(Cfg::Freebsd11),
12 => cfgs.push(Cfg::Freebsd12),
13 => cfgs.push(Cfg::Freebsd13),
14 => cfgs.push(Cfg::Freebsd14),
_ => cfgs.push(Cfg::Freebsd15),
match which_freebsd {
x if x < 10 => panic!("FreeBSD older than 10 is not supported"),
10 => cfgs.push(Cfg::Freebsd10),
11 => cfgs.push(Cfg::Freebsd11),
12 => cfgs.push(Cfg::Freebsd12),
13 => cfgs.push(Cfg::Freebsd13),
14 => cfgs.push(Cfg::Freebsd14),
_ => cfgs.push(Cfg::Freebsd15),
}
}

match emcc_version_code() {
Some(v) if (v < 30142) => cfgs.push(Cfg::EmscriptenOldStatAbi),
// Non-Emscripten or version >= 3.1.42.
_ => (),
if target_os == "emscripten" {
match emcc_version_code() {
Some(v) if (v < 30142) => cfgs.push(Cfg::EmscriptenOldStatAbi),
// Non-Emscripten or version >= 3.1.42.
_ => (),
}
}

match vxworks_version_code() {
Some(v) if (v < (25, 9)) => cfgs.push(Cfg::VxworksLt25_09),
// VxWorks version >= 25.09
_ => (),
if target_os == "vxworks" {
match vxworks_version_code() {
Some(v) if (v < (25, 9)) => cfgs.push(Cfg::VxworksLt25_09),
// VxWorks version >= 25.09
_ => (),
}
}

let mut musl_v1_2 = env_flag("CARGO_CFG_LIBC_UNSTABLE_MUSL_V1_2");
Expand Down Expand Up @@ -294,7 +301,9 @@ fn main() {
};

if timebits == "64" {
cfgs.push(Cfg::LinuxTimeBits64);
if target_os == "linux" {
cfgs.push(Cfg::LinuxTimeBits64);
}
cfgs.push(Cfg::GnuFileOffsetBits64);
cfgs.push(Cfg::GnuTimeBits64);
}
Expand All @@ -319,6 +328,7 @@ fn main() {

cfgs.sort_unstable();
cfgs.dedup();
validate_cfg(&cfgs, &target_env, &target_os, &target_ptr_width);

for cfg in cfgs {
set_cfg(cfg);
Expand Down Expand Up @@ -403,6 +413,84 @@ fn rustc_minor_nightly() -> (u32, bool) {
(minor, nightly)
}

/// Check that our list of cfg makes sense for the current target.
fn validate_cfg(list: &[Cfg], target_env: &str, target_os: &str, target_ptr_width: &str) {
for cfg in list {
match cfg {
Cfg::LibcDenyWarnings => (),
Cfg::LibcElfv2 => (),
Cfg::LibcPauthtest => (),
Cfg::EspidfPicolibc => (),
Cfg::EspidfTime32 => (),

Cfg::EmscriptenOldStatAbi => {
assert_eq!(
target_os, "emscripten",
"{cfg:?} set on non-freebsd platform"
);
}

Cfg::Freebsd10
| Cfg::Freebsd11
| Cfg::Freebsd12
| Cfg::Freebsd13
| Cfg::Freebsd14
| Cfg::Freebsd15 => {
assert_eq!(target_os, "freebsd", "{cfg:?} set on non-freebsd platform");
}

Cfg::VxworksLt25_09 => {
assert_eq!(target_os, "vxworks", "{cfg:?} set on non-vxworks platform");
}

Cfg::GnuFileOffsetBits64 => {
assert_eq!(target_env, "gnu", "{cfg:?} set on non-gnu platform");
assert_eq!(target_ptr_width, "32", "{cfg:?} set on non-32-bit platform");
}
Cfg::GnuTimeBits64 => {
assert_eq!(target_env, "gnu", "{cfg:?} set on non-gnu platform");
assert_eq!(target_ptr_width, "32", "{cfg:?} set on non-32-bit platform");
assert!(
list.contains(&Cfg::GnuFileOffsetBits64),
"{cfg:?} set without 64-bit off_t"
)
}
Cfg::LinuxTimeBits64 => {
assert_eq!(target_os, "linux", "{cfg:?} set on non-linux platform");
assert_eq!(target_ptr_width, "32", "{cfg:?} set on non-32-bit platform");
}
Cfg::MuslV1_2 => {
assert!(
matches!(target_env, "musl" | "ohos"),
"{cfg:?} set with env {target_env}"
);
}
Cfg::Musl32Time64 => {
assert!(
matches!(target_env, "musl" | "ohos"),
"{cfg:?} set with env {target_env}"
);
assert_eq!(target_ptr_width, "32", "{cfg:?} set on non-32-bit platform");
assert!(
list.contains(&Cfg::MuslV1_2),
"{cfg:?} set on non-musl1.2 platform"
)
}
Cfg::MuslRedirTime64 => {
assert!(
matches!(target_env, "musl" | "ohos"),
"{cfg:?} set with env {target_env}"
);
assert_eq!(target_ptr_width, "32", "{cfg:?} set on non-32-bit platform");
assert!(
list.contains(&Cfg::MuslV1_2),
"{cfg:?} set on non-musl1.2 platform"
)
}
}
}
}

fn which_freebsd() -> Option<i32> {
let output = Command::new("freebsd-version").output().ok()?;
if !output.status.success() {
Expand Down
6 changes: 5 additions & 1 deletion etc/libc-util.py
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
import shlex
import subprocess as sp
import sys
import time
from dataclasses import dataclass
from enum import StrEnum
from inspect import cleandoc
Expand Down Expand Up @@ -477,6 +478,8 @@ def check_all_targets(
failures = []
matched_only_already_skipped = []

start = time.time()

if only is not None:
for t in checks:
if t.pattern_matches(only):
Expand Down Expand Up @@ -554,8 +557,9 @@ def check_all_targets(
if len(failures) > self.failure_limit:
break

elapsed = round(time.time() - start, 2)
print(
f"finished checking {ran} targets. {passed} passed, "
f"finished checking {ran} targets in {elapsed} seconds. {passed} passed, "
f"{len(failures)} failed, {skipped} skipped"
)
if len(matched_only_already_skipped) > 0:
Expand Down
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