gnu: build settings for _FILE_OFFSET_BITS=64

Author: snogge

build.rs

@@ -13,6 +13,8 @@ const ALLOWED_CFGS: &'static [&'static str] = &[
     "freebsd13",
     "freebsd14",
     "freebsd15",
+    // Corresponds to `_FILE_OFFSET_BITS=64` in glibc
+    "gnu_file_offset_bits64",
     // FIXME(ctest): this config shouldn't be needed but ctest can't parse `const extern fn`
     "libc_const_extern_fn",
     "libc_deny_warnings",
@@ -84,6 +86,26 @@ fn main() {
     if linux_time_bits64 {
         set_cfg("linux_time_bits64");
     }
+    println!("cargo:rerun-if-env-changed=RUST_LIBC_UNSTABLE_GNU_FILE_OFFSET_BITS64");
+    match env::var("RUST_LIBC_UNSTABLE_GNU_FILE_OFFSET_BITS64") {
+        Ok(val) => {
+            if val == "1" {
+                let target_env = env::var("CARGO_CFG_TARGET_ENV").unwrap();
+                let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
+                let target_ptr_width = env::var("CARGO_CFG_TARGET_POINTER_WIDTH").unwrap();
+                let target_arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
+                if target_env == "gnu"
+                    && target_os == "linux"
+                    && target_ptr_width == "32"
+                    && target_arch != "riscv32"
+                    && target_arch != "x86_64"
+                {
+                    set_cfg("gnu_file_offset_bits64");
+                }
+            }
+        }
+        Err(_e) => {}
+    }
 
     // On CI: deny all warnings
     if libc_ci {

libc-test/build.rs

@@ -3574,6 +3574,25 @@ fn test_vxworks(target: &str) {
     cfg.generate(src_hotfix_dir().join("lib.rs"), "main.rs");
 }
 
+fn config_gnu_bits(target: &str, cfg: &mut ctest::TestGenerator) {
+    match env::var("RUST_LIBC_UNSTABLE_GNU_FILE_OFFSET_BITS64") {
+        Ok(val) => {
+            if val == "1" {
+                if target.contains("gnu")
+                    && target.contains("linux")
+                    && !target.ends_with("x32")
+                    && !target.contains("riscv32")
+                    && env::var("CARGO_CFG_TARGET_POINTER_WIDTH").unwrap() == "32"
+                {
+                    cfg.define("_FILE_OFFSET_BITS", Some("64"));
+                    cfg.cfg("gnu_file_offset_bits64", None);
+                }
+            }
+        }
+        Err(_e) => {}
+    }
+}
+
 fn test_linux(target: &str) {
     assert!(target.contains("linux"));
 
@@ -3617,6 +3636,8 @@ fn test_linux(target: &str) {
     // glibc versions older than 2.29.
     cfg.define("__GLIBC_USE_DEPRECATED_SCANF", None);
 
+    config_gnu_bits(target, &mut cfg);
+
     headers! { cfg:
                "ctype.h",
                "dirent.h",
@@ -4064,8 +4085,7 @@ fn test_linux(target: &str) {
             "epoll_params" => true,
 
             // FIXME(linux): Requires >= 6.12 kernel headers.
-            "dmabuf_cmsg" |
-            "dmabuf_token" => true,
+            "dmabuf_cmsg" | "dmabuf_token" => true,
 
             _ => false,
         }
@@ -4779,6 +4799,7 @@ fn test_linux_like_apis(target: &str) {
     if linux || android || emscripten {
         // test strerror_r from the `string.h` header
         let mut cfg = ctest_cfg();
+        config_gnu_bits(target, &mut cfg);
         cfg.skip_type(|_| true).skip_static(|_| true);
 
         headers! { cfg: "string.h" }
@@ -4795,6 +4816,7 @@ fn test_linux_like_apis(target: &str) {
         // test fcntl - see:
         // http://man7.org/linux/man-pages/man2/fcntl.2.html
         let mut cfg = ctest_cfg();
+        config_gnu_bits(target, &mut cfg);
 
         if musl {
             cfg.header("fcntl.h");
@@ -4824,6 +4846,7 @@ fn test_linux_like_apis(target: &str) {
     if (linux && !wali) || android {
         // test termios
         let mut cfg = ctest_cfg();
+        config_gnu_bits(target, &mut cfg);
         cfg.header("asm/termbits.h");
         cfg.header("linux/termios.h");
         cfg.skip_type(|_| true)
@@ -4848,6 +4871,7 @@ fn test_linux_like_apis(target: &str) {
     if linux || android {
         // test IPV6_ constants:
         let mut cfg = ctest_cfg();
+        config_gnu_bits(target, &mut cfg);
         headers! {
             cfg:
             "linux/in6.h"
@@ -4879,6 +4903,7 @@ fn test_linux_like_apis(target: &str) {
         // "resolve.h" defines a `p_type` macro that expands to `__p_type`
         // making the tests for these fails when both are included.
         let mut cfg = ctest_cfg();
+        config_gnu_bits(target, &mut cfg);
         cfg.header("elf.h");
         cfg.skip_fn(|_| true)
             .skip_static(|_| true)
@@ -4898,6 +4923,7 @@ fn test_linux_like_apis(target: &str) {
     if (linux && !wali) || android {
         // Test `ARPHRD_CAN`.
         let mut cfg = ctest_cfg();
+        config_gnu_bits(target, &mut cfg);
         cfg.header("linux/if_arp.h");
         cfg.skip_fn(|_| true)
             .skip_static(|_| true)