WasmVM: realloc(ptr, 0) returns non-NULL instead of NULL per POSIX #32
Description
Summary
realloc(ptr, 0) returns a non-NULL pointer in WASM (WASI libc / dlmalloc) but returns NULL on native Linux (glibc). POSIX allows either behavior, but the os-test suite expects NULL.
Affected os-test cases
malloc/realloc-0
Expected behavior
realloc(ptr, 0) should return NULL to match glibc behavior and os-test expectations.
Context
This is a WASI sysroot (dlmalloc) behavioral difference. Discovered via os-test POSIX conformance suite. Tracked in posix-exclusions.json as fail / patched-sysroot.