C: sizeof(array-type) ignores the array extent

• Type: bug (Track C — C frontend, ParseCSizeof / ParseCDeclType in cparser.inc). Silent wrong value.
• Found: 2026-07-18, gcc-differential sweep.

Repro

#include <stdio.h>
int main(void){
  printf("%lu %lu %lu %lu\n",
    sizeof(int[10]), sizeof(char[5]), sizeof(int[2][3]), sizeof(double[4]));
  return 0;
}

• gcc: 40 5 24 32.
• pxx: 4 1 4 8 — every sizeof(TYPE[N]) returns just the ELEMENT size; the array extent(s) are dropped.

Root

ParseCSizeof type branch does tk := ParseCDeclType; sz := CTypeSizeBytes(tk). ParseCDeclType captures a trailing [N] only for typedef-inherent arrays (CTypeTypedefArrLen) and pointer-to-array declarators — NOT for an abstract array type-name like int[10], so the extent never reaches the size calc. (Same missing "abstract-array-extent capture" as [[bug-c-pointer-to-multidim-array-declarator]].)

Fix direction

Have ParseCDeclType record an abstract trailing [N][M].. dim list; in the sizeof type branch multiply CTypeSizeBytes(tk) by the product of the extents. Rare in real code (usually sizeof(var) / sizeof(type)), but silent.

Acceptance

• The repro prints 40 5 24 32; C-conformance 220/220 + self-host byte-identical.
• A test/*.c regression.

Log

• 2026-07-18 — resolved, commit ec713264.