Increase MSRV to 1.38 and use ptr.cast::<T>() whenever practical to clarify casts. (#425)

Avoid anonymous type casts of the form `as *{const,mut} _`.

Make it clearer that we're never casting away constness by avoiding `as
*mut T` whenever practical.

Author: briansmith

.clippy.toml

@@ -1 +1 @@
-msrv = "1.36"
+msrv = "1.38"

.github/workflows/tests.yml

@@ -44,7 +44,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-22.04, windows-2022]
-        toolchain: [nightly, beta, stable, 1.36]
+        toolchain: [nightly, beta, stable, 1.38]
         # Only Test macOS on stable to reduce macOS CI jobs
         include:
           # x86_64-apple-darwin.

CHANGELOG.md

@@ -4,6 +4,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Breaking Changes
+- Update MSRV to 1.38 [#425]
+
+[#425]: https://github.com/rust-random/getrandom/pull/425
+
 ## [0.2.15] - 2024-05-06
 ### Added
 - Apple visionOS support [#410]

README.md

@@ -52,7 +52,7 @@ crate features, WASM support and Custom RNGs see the
 
 ## Minimum Supported Rust Version
 
-This crate requires Rust 1.36.0 or later.
+This crate requires Rust 1.38.0 or later.
 
 ## Platform Support
 

src/apple-other.rs

@@ -14,7 +14,7 @@ extern "C" {
 }
 
 pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
-    let ret = unsafe { CCRandomGenerateBytes(dest.as_mut_ptr() as *mut c_void, dest.len()) };
+    let ret = unsafe { CCRandomGenerateBytes(dest.as_mut_ptr().cast::<c_void>(), dest.len()) };
     // kCCSuccess (from CommonCryptoError.h) is always zero.
     if ret != 0 {
         Err(Error::IOS_SEC_RANDOM)

src/error.rs

@@ -99,7 +99,7 @@ impl Error {
 cfg_if! {
     if #[cfg(unix)] {
         fn os_err(errno: i32, buf: &mut [u8]) -> Option<&str> {
-            let buf_ptr = buf.as_mut_ptr() as *mut libc::c_char;
+            let buf_ptr = buf.as_mut_ptr().cast::<libc::c_char>();
             if unsafe { libc::strerror_r(errno, buf_ptr, buf.len()) } != 0 {
                 return None;
             }

src/fuchsia.rs

@@ -8,6 +8,6 @@ extern "C" {
 }
 
 pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
-    unsafe { zx_cprng_draw(dest.as_mut_ptr() as *mut u8, dest.len()) }
+    unsafe { zx_cprng_draw(dest.as_mut_ptr().cast::<u8>(), dest.len()) }
     Ok(())
 }

src/getentropy.rs

@@ -8,11 +8,11 @@
 //!
 //! For these targets, we use getentropy(2) because getrandom(2) doesn't exist.
 use crate::{util_libc::last_os_error, Error};
-use core::mem::MaybeUninit;
+use core::{ffi::c_void, mem::MaybeUninit};
 
 pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
     for chunk in dest.chunks_mut(256) {
-        let ret = unsafe { libc::getentropy(chunk.as_mut_ptr() as *mut libc::c_void, chunk.len()) };
+        let ret = unsafe { libc::getentropy(chunk.as_mut_ptr().cast::<c_void>(), chunk.len()) };
         if ret != 0 {
             return Err(last_os_error());
         }

src/getrandom.rs

@@ -16,10 +16,10 @@
 //! nothing. On illumos, the default pool is used to implement getentropy(2),
 //! so we assume it is acceptable here.
 use crate::{util_libc::sys_fill_exact, Error};
-use core::mem::MaybeUninit;
+use core::{ffi::c_void, mem::MaybeUninit};
 
 pub fn getrandom_inner(dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
     sys_fill_exact(dest, |buf| unsafe {
-        libc::getrandom(buf.as_mut_ptr() as *mut libc::c_void, buf.len(), 0)
+        libc::getrandom(buf.as_mut_ptr().cast::<c_void>(), buf.len(), 0)
     })
 }

src/hermit.rs

@@ -13,7 +13,7 @@ extern "C" {
 
 pub fn getrandom_inner(mut dest: &mut [MaybeUninit<u8>]) -> Result<(), Error> {
     while !dest.is_empty() {
-        let res = unsafe { sys_read_entropy(dest.as_mut_ptr() as *mut u8, dest.len(), 0) };
+        let res = unsafe { sys_read_entropy(dest.as_mut_ptr().cast::<u8>(), dest.len(), 0) };
         // Positive `isize`s can be safely casted to `usize`
         if res > 0 && (res as usize) <= dest.len() {
             dest = &mut dest[res as usize..];