Don't assume the size when allocating a CFNumber #977
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CoreFoundation assumed the size of a `struct __CFNumber` (which contains a `CFRuntimeBase` and an `int64_t`) would be the size of a `CFRuntimeBase` plus 8 bytes. This assumption may be true on some platforms, but on my Raspberry Pi, the size of a `CFRuntimeBase` was 20 bytes. The compiler inserted four bytes of padding before the `int64_t` to align it to an 8-byte boundary, causing the structure to take up 32 bytes instead of the 28 bytes the code allocated. Writing to the `int64_t` overwrote some of `malloc`'s internal bookkeeping information and caused a crash. I changed the code to use a couple of `sizeof`s to calculate the extra space to allocate, like the rest of CoreFoundation does (see [this search](https://github.com/apple/swift-corelibs-foundation/search?utf8=✓&q=_CFRuntimeCreateInstance&type=)).
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Looks good, thanks. |
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@swift-ci test and merge |
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CoreFoundation assumed the size of a
struct __CFNumber(which contains aCFRuntimeBaseand anint64_t) would be the size of aCFRuntimeBaseplus 8 bytes.This assumption may be true on some platforms, but on my Raspberry Pi, the size of a
CFRuntimeBasewas 20 bytes. The compiler inserted four bytes of padding before theint64_tto align it to an 8-byte boundary, causing the structure to take up 32 bytes instead of the 28 bytes the code allocated. Writing to theint64_toverwrote some ofmalloc's internal bookkeeping information and caused a crash.I changed the code to use a couple of
sizeofs to calculate the extra space to allocate, like the rest of CoreFoundation does (see this search).