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rust: do not assume realloc preserves alignment

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Signed-off-by: Ferdinand Bachmann <theferdi265@gmail.com>
This commit is contained in:
Ferdinand Bachmann 2022-03-09 23:17:28 +01:00 committed by Hector Martin
parent d161de0037
commit 5983d997d8
1 changed files with 25 additions and 3 deletions
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28
rust/src/dlmalloc.rs
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@ -7,7 +7,7 @@ use cty::*;
extern "C" {
pub fn malloc(size: size_t) -> *mut c_void;
pub fn realloc(p: *mut c_void, size: size_t) -> *mut c_void;
pub fn realloc_in_place(p: *mut c_void, size: size_t) -> *mut c_void;
pub fn free(p: *mut c_void);
pub fn posix_memalign(p: *mut *mut c_void, alignment: size_t, size: size_t) -> c_int;
}
@ -51,7 +51,29 @@ unsafe impl GlobalAlloc for DLMalloc {
}
#[inline]
unsafe fn realloc(&self, ptr: *mut u8, _layout: Layout, new_size: usize) -> *mut u8 {
unsafe { realloc(ptr as *mut c_void, new_size) as *mut u8 }
unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
// Unfortunately, realloc doesn't make any alignment guarantees, so the memory
// has to be manually allocated as aligned memory if it cannot be resized
// in-place.
let mut new_ptr = unsafe { realloc_in_place(ptr as *mut c_void, new_size) as *mut u8 };
// return early if in-place resize succeeded
if !new_ptr.is_null() {
return new_ptr;
}
// allocate new aligned storage with correct layout
new_ptr =
unsafe { self.alloc(Layout::from_size_align_unchecked(new_size, layout.align())) };
// return early if allocation failed
if new_ptr.is_null() {
return ptr::null_mut();
}
// copy over the data and deallocate the old storage
unsafe { ptr::copy(ptr, new_ptr, layout.size().min(new_size)) };
unsafe { self.dealloc(ptr, layout) };
new_ptr
}
}