From e7772f20881282ede329ed2c19eb479fded4aecd Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Sun, 19 May 2024 14:58:48 +0200 Subject: [PATCH 1/2] use posix_memalign on most Unix targets --- library/std/src/sys/pal/unix/alloc.rs | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/library/std/src/sys/pal/unix/alloc.rs b/library/std/src/sys/pal/unix/alloc.rs index 2f908e3d0e9..242a054199f 100644 --- a/library/std/src/sys/pal/unix/alloc.rs +++ b/library/std/src/sys/pal/unix/alloc.rs @@ -59,10 +59,9 @@ unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut } cfg_if::cfg_if! { - // We use posix_memalign wherever possible, but not all targets have that function. + // We use posix_memalign wherever possible, but some targets have very incomplete POSIX coverage + // so we need a fallback for those. if #[cfg(any( - target_os = "redox", - target_os = "espidf", target_os = "horizon", target_os = "vita", ))] { @@ -74,12 +73,11 @@ unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { #[inline] unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { let mut out = ptr::null_mut(); - // We prefer posix_memalign over aligned_malloc since with aligned_malloc, - // implementations are making almost arbitrary choices for which alignments are - // "supported", making it hard to use. For instance, some implementations require the - // size to be a multiple of the alignment (wasi emmalloc), while others require the - // alignment to be at least the pointer size (Illumos, macOS) -- which may or may not be - // standards-compliant, but that does not help us. + // We prefer posix_memalign over aligned_malloc since it is more widely available, and + // since with aligned_malloc, implementations are making almost arbitrary choices for + // which alignments are "supported", making it hard to use. For instance, some + // implementations require the size to be a multiple of the alignment (wasi emmalloc), + // while others require the alignment to be at least the pointer size (Illumos, macOS). // posix_memalign only has one, clear requirement: that the alignment be a multiple of // `sizeof(void*)`. Since these are all powers of 2, we can just use max. let align = layout.align().max(crate::mem::size_of::()); From 3c2d9c2dbe0fd764b4af473a75fb4f44616f6b4c Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Sun, 19 May 2024 20:40:46 +0200 Subject: [PATCH 2/2] fix typo Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com> --- library/std/src/sys/pal/unix/alloc.rs | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/library/std/src/sys/pal/unix/alloc.rs b/library/std/src/sys/pal/unix/alloc.rs index 242a054199f..eb3a57c212b 100644 --- a/library/std/src/sys/pal/unix/alloc.rs +++ b/library/std/src/sys/pal/unix/alloc.rs @@ -73,8 +73,8 @@ unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { #[inline] unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { let mut out = ptr::null_mut(); - // We prefer posix_memalign over aligned_malloc since it is more widely available, and - // since with aligned_malloc, implementations are making almost arbitrary choices for + // We prefer posix_memalign over aligned_alloc since it is more widely available, and + // since with aligned_alloc, implementations are making almost arbitrary choices for // which alignments are "supported", making it hard to use. For instance, some // implementations require the size to be a multiple of the alignment (wasi emmalloc), // while others require the alignment to be at least the pointer size (Illumos, macOS).