Bump MSRV to 1.31

This permits `Cargo.toml` to include optional dependencies. On toolchains earlier than 1.31, the optional dependency syntax is not supported. With the MSRV at 1.31, any optional dependency may be supported even if *its* MSRV is higher than *our* MSRV since only users using a more recent toolchain will enable that dependency. In particular, this paves the way for adding an optional `zerocopy` dependency (prototyped in #3407 and #3914; see also google/zerocopy#557), which permits many uses of libc to no longer require `unsafe` code.
rust-lang · Sep 14, 2024 · 2ff5d5c · 2ff5d5c
1 parent a515d07
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diff --git a/.github/workflows/full_ci.yml b/.github/workflows/full_ci.yml
@@ -154,13 +154,7 @@ jobs:
           stable,
           beta,
           nightly,
-          # FIXME: Disabled due to:
-          # error: failed to parse registry's information for: serde
-          #1.13.0,
-          1.19.0,
-          1.24.0,
-          1.25.0,
-          1.30.0,
+          1.31.0,
         ]
     steps:
       - uses: actions/checkout@v4
@@ -205,10 +199,6 @@ jobs:
       fail-fast: true
       matrix:
         toolchain: [
-          1.19.0,
-          1.24.0,
-          1.25.0,
-          1.30.0,
           stable,
         ]
     steps:

diff --git a/README.md b/README.md
@@ -51,18 +51,13 @@ libc = "0.2"
 
 ## Rust version support
 
-The minimum supported Rust toolchain version is currently **Rust 1.13.0**.
+The minimum supported Rust toolchain version is currently **Rust 1.31.0**.
 (libc does not currently have any policy regarding changes to the minimum
 supported Rust version; such policy is a work in progress.) APIs requiring
 newer Rust features are only available on newer Rust toolchains:
 
 | Feature              | Version |
 |----------------------|---------|
-| `union`              |  1.19.0 |
-| `const mem::size_of` |  1.24.0 |
-| `repr(align)`        |  1.25.0 |
-| `extra_traits`       |  1.25.0 |
-| `core::ffi::c_void`  |  1.30.0 |
 | `repr(packed(N))`    |  1.33.0 |
 | `cfg(target_vendor)` |  1.33.0 |
 | `const-extern-fn`    |  1.62.0 |

diff --git a/build-tmp.rs b/build-tmp.rs
@@ -15,22 +15,16 @@ const ALLOWED_CFGS: &'static [&'static str] = &[
     "freebsd13",
     "freebsd14",
     "freebsd15",
-    "libc_align",
     "libc_cfg_target_vendor",
     "libc_const_extern_fn",
     "libc_const_extern_fn_unstable",
-    "libc_const_size_of",
-    "libc_core_cvoid",
     "libc_deny_warnings",
-    "libc_int128",
     "libc_long_array",
     "libc_non_exhaustive",
     "libc_packedN",
-    "libc_priv_mod_use",
     "libc_ptr_addr_of",
     "libc_thread_local",
     "libc_underscore_const_names",
-    "libc_union",
     "libc_ctest",
 ];
 
@@ -95,38 +89,6 @@ fn main() {
         set_cfg("libc_deny_warnings");
     }
 
-    // Rust >= 1.15 supports private module use:
-    if rustc_minor_ver >= 15 || rustc_dep_of_std {
-        set_cfg("libc_priv_mod_use");
-    }
-
-    // Rust >= 1.19 supports unions:
-    if rustc_minor_ver >= 19 || rustc_dep_of_std {
-        set_cfg("libc_union");
-    }
-
-    // Rust >= 1.24 supports const mem::size_of:
-    if rustc_minor_ver >= 24 || rustc_dep_of_std {
-        set_cfg("libc_const_size_of");
-    }
-
-    // Rust >= 1.25 supports repr(align):
-    if rustc_minor_ver >= 25 || rustc_dep_of_std || align_cargo_feature {
-        set_cfg("libc_align");
-    }
-
-    // Rust >= 1.26 supports i128 and u128:
-    if rustc_minor_ver >= 26 || rustc_dep_of_std {
-        set_cfg("libc_int128");
-    }
-
-    // Rust >= 1.30 supports `core::ffi::c_void`, so libc can just re-export it.
-    // Otherwise, it defines an incompatible type to retaining
-    // backwards-compatibility.
-    if rustc_minor_ver >= 30 || rustc_dep_of_std {
-        set_cfg("libc_core_cvoid");
-    }
-
     // Rust >= 1.33 supports repr(packed(N)) and cfg(target_vendor).
     if rustc_minor_ver >= 33 || rustc_dep_of_std {
         set_cfg("libc_packedN");

diff --git a/build.rs b/build.rs
@@ -14,22 +14,16 @@ const ALLOWED_CFGS: &'static [&'static str] = &[
     "freebsd13",
     "freebsd14",
     "freebsd15",
-    "libc_align",
     "libc_cfg_target_vendor",
     "libc_const_extern_fn",
     "libc_const_extern_fn_unstable",
-    "libc_const_size_of",
-    "libc_core_cvoid",
     "libc_deny_warnings",
-    "libc_int128",
     "libc_long_array",
     "libc_non_exhaustive",
     "libc_packedN",
-    "libc_priv_mod_use",
     "libc_ptr_addr_of",
     "libc_thread_local",
     "libc_underscore_const_names",
-    "libc_union",
     "libc_ctest",
 ];
 
@@ -49,7 +43,6 @@ fn main() {
 
     let (rustc_minor_ver, is_nightly) = rustc_minor_nightly();
     let rustc_dep_of_std = env::var("CARGO_FEATURE_RUSTC_DEP_OF_STD").is_ok();
-    let align_cargo_feature = env::var("CARGO_FEATURE_ALIGN").is_ok();
     let const_extern_fn_cargo_feature = env::var("CARGO_FEATURE_CONST_EXTERN_FN").is_ok();
     let libc_ci = env::var("LIBC_CI").is_ok();
     let libc_check_cfg = env::var("LIBC_CHECK_CFG").is_ok() || rustc_minor_ver >= 80;
@@ -94,38 +87,6 @@ fn main() {
         set_cfg("libc_deny_warnings");
     }
 
-    // Rust >= 1.15 supports private module use:
-    if rustc_minor_ver >= 15 || rustc_dep_of_std {
-        set_cfg("libc_priv_mod_use");
-    }
-
-    // Rust >= 1.19 supports unions:
-    if rustc_minor_ver >= 19 || rustc_dep_of_std {
-        set_cfg("libc_union");
-    }
-
-    // Rust >= 1.24 supports const mem::size_of:
-    if rustc_minor_ver >= 24 || rustc_dep_of_std {
-        set_cfg("libc_const_size_of");
-    }
-
-    // Rust >= 1.25 supports repr(align):
-    if rustc_minor_ver >= 25 || rustc_dep_of_std || align_cargo_feature {
-        set_cfg("libc_align");
-    }
-
-    // Rust >= 1.26 supports i128 and u128:
-    if rustc_minor_ver >= 26 || rustc_dep_of_std {
-        set_cfg("libc_int128");
-    }
-
-    // Rust >= 1.30 supports `core::ffi::c_void`, so libc can just re-export it.
-    // Otherwise, it defines an incompatible type to retaining
-    // backwards-compatibility.
-    if rustc_minor_ver >= 30 || rustc_dep_of_std {
-        set_cfg("libc_core_cvoid");
-    }
-
     // Rust >= 1.33 supports repr(packed(N)) and cfg(target_vendor).
     if rustc_minor_ver >= 33 || rustc_dep_of_std {
         set_cfg("libc_packedN");

diff --git a/ci/build.sh b/ci/build.sh
@@ -169,15 +169,9 @@ case "${OS}" in
     linux*)
         TARGETS="${RUST_LINUX_TARGETS}"
 
-        if [ "${RUST}" != "1.13.0" ]; then
-            TARGETS="${TARGETS} ${RUST_GT_1_13_LINUX_TARGETS}"
-            if [ "${RUST}" != "1.19.0" ]; then
-                TARGETS="${TARGETS} ${RUST_GT_1_19_LINUX_TARGETS}"
-                if [ "${RUST}" != "1.24.0" ]; then
-                    TARGETS="${TARGETS} ${RUST_GT_1_24_LINUX_TARGETS}"
-                fi
-            fi
-        fi
+        TARGETS="${TARGETS} ${RUST_GT_1_13_LINUX_TARGETS}"
+        TARGETS="${TARGETS} ${RUST_GT_1_19_LINUX_TARGETS}"
+        TARGETS="${TARGETS} ${RUST_GT_1_24_LINUX_TARGETS}"
 
         if [ "${RUST}" = "nightly" ]; then
             TARGETS="${TARGETS} ${RUST_NIGHTLY_LINUX_TARGETS}"

diff --git a/libc-test/build.rs b/libc-test/build.rs
@@ -68,15 +68,7 @@ fn do_ctest() {
 
 fn ctest_cfg() -> ctest::TestGenerator {
     let mut cfg = ctest::TestGenerator::new();
-    let libc_cfgs = [
-        "libc_priv_mod_use",
-        "libc_union",
-        "libc_const_size_of",
-        "libc_align",
-        "libc_core_cvoid",
-        "libc_packedN",
-        "libc_thread_local",
-    ];
+    let libc_cfgs = ["libc_packedN", "libc_thread_local"];
     for f in &libc_cfgs {
         cfg.cfg(f, None);
     }

diff --git a/src/fixed_width_ints.rs b/src/fixed_width_ints.rs
@@ -20,7 +20,7 @@ pub type uint32_t = u32;
 pub type uint64_t = u64;
 
 cfg_if! {
-    if #[cfg(all(libc_int128, target_arch = "aarch64", not(target_os = "windows")))] {
+    if #[cfg(all(target_arch = "aarch64", not(target_os = "windows")))] {
         // This introduces partial support for FFI with __int128 and
         // equivalent types on platforms where Rust's definition is validated
         // to match the standard C ABI of that platform.

diff --git a/src/fuchsia/mod.rs b/src/fuchsia/mod.rs
@@ -4362,33 +4362,8 @@ cfg_if! {
     }
 }
 
-cfg_if! {
-    if #[cfg(libc_align)] {
-        #[macro_use]
-        mod align;
-    } else {
-        #[macro_use]
-        mod no_align;
-    }
-}
+#[macro_use]
+mod align;
 expand_align!();
 
-cfg_if! {
-    if #[cfg(libc_core_cvoid)] {
-        pub use ::ffi::c_void;
-    } else {
-        // Use repr(u8) as LLVM expects `void*` to be the same as `i8*` to help
-        // enable more optimization opportunities around it recognizing things
-        // like malloc/free.
-        #[repr(u8)]
-        #[allow(missing_copy_implementations)]
-        #[allow(missing_debug_implementations)]
-        pub enum c_void {
-            // Two dummy variants so the #[repr] attribute can be used.
-            #[doc(hidden)]
-            __variant1,
-            #[doc(hidden)]
-            __variant2,
-        }
-    }
-}
+pub use ffi::c_void;
diff --git a/src/fuchsia/no_align.rs b/src/fuchsia/no_align.rs