From 1b0bb35ca3cd8e80c9255eefb1e35381ec9aa73a Mon Sep 17 00:00:00 2001 From: Remy Rakic Date: Fri, 28 Feb 2020 12:22:28 +0100 Subject: [PATCH] Unrevert "Remove `checked_add` in `Layout::repeat`" --- src/libcore/alloc.rs | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) diff --git a/src/libcore/alloc.rs b/src/libcore/alloc.rs index a04e75bc7ce7c..71f7f971eabaf 100644 --- a/src/libcore/alloc.rs +++ b/src/libcore/alloc.rs @@ -241,13 +241,11 @@ impl Layout { #[unstable(feature = "alloc_layout_extra", issue = "55724")] #[inline] pub fn repeat(&self, n: usize) -> Result<(Self, usize), LayoutErr> { - // Warning, removing the checked_add here led to segfaults in #67174. Further - // analysis in #69225 seems to indicate that this is an LTO-related - // miscompilation, so #67174 might be able to be reapplied in the future. - let padded_size = self - .size() - .checked_add(self.padding_needed_for(self.align())) - .ok_or(LayoutErr { private: () })?; + // This cannot overflow. Quoting from the invariant of Layout: + // > `size`, when rounded up to the nearest multiple of `align`, + // > must not overflow (i.e., the rounded value must be less than + // > `usize::MAX`) + let padded_size = self.size() + self.padding_needed_for(self.align()); let alloc_size = padded_size.checked_mul(n).ok_or(LayoutErr { private: () })?; unsafe {