unsafeNew(UncheckedArrayXxx) does not calculate the size of sizeof(dummy). #22556
Description
Description
I allocated 10 bytes of memory, one byte occupied by the dummy field.
type
ChunkObj = object
data: UncheckedArray[byte]
proc alloc(size: int): ref ChunkObj =
unsafeNew(result, size)
proc main() =
let buf = alloc(10)
buf.data[9] = 100 # index out of bounds, because one byte is occupied by the 'dummy' field,
# the actual usable size of data is 9 bytesstruct tyObject_ChunkObj__mOTFrUaGXmv4xFi10w76AA {
char dummy; // one byte
NU8 data[SEQ_DECL_SIZE];
};Here is the C code for the alloc function:
N_LIB_PRIVATE N_NIMCALL(tyObject_ChunkObj__mOTFrUaGXmv4xFi10w76AA*, alloc__spaces_u3)(NI size_p0) {
tyObject_ChunkObj__mOTFrUaGXmv4xFi10w76AA* result;
nimfr_("alloc", "/root/repos/spaces/src/spaces.nim");
{ result = NIM_NIL;
nimln_(11); eqdestroy___spaces_u32(result);
if ((size_p0) < ((NI)0) || (size_p0) > ((NI)IL64(9223372036854775807))){ raiseRangeErrorI(size_p0, ((NI)0), ((NI)IL64(9223372036854775807))); goto BeforeRet_;
}
result = (tyObject_ChunkObj__mOTFrUaGXmv4xFi10w76AA*) nimNewObj(((NI) (size_p0)), NIM_ALIGNOF(tyObject_ChunkObj__mOTFrUaGXmv4xFi10w76AA));
}BeforeRet_: ;
popFrame();
return result;
}size_p0 is the size of memory I want to allocate, which is 10, and the value of sizeof(dummy) should be added when calling the 'nimNewObj' function.
Nim Version
Nim Compiler Version 2.1.1 [Linux: amd64]
Compiled at 2023-08-23
Copyright (c) 2006-2023 by Andreas Rumpf
git hash: 6b04d03
active boot switches: -d:release
Current Output
no output, no exception
Expected Output
no output, no exception
Possible Solution
Add the value of sizeof(dummy) before calling the unsafeNew function.
For compatibility reasons, I used offsetof(ChunkObj, data), but offsetof(ChunkObj, data) didn't work, see #22553
Additional Information
No response