Summary
On wasm32-hwjs the C library and the compiler disagree on the underlying type
of size_t, which makes it impossible to build any C++ / libc++ for the target.
- Compiler (fork clang,
wasm32-hwjs-linux-musl):__SIZE_TYPE__ = long unsigned int(unsigned long). - musl (
arch/wasm32/bits/alltypes.h.in):#define _Addr int→typedef unsigned _Addr size_t;=unsigned int.
Both are 4 bytes on wasm32, but they are distinct types. Clang special-cases
the replaceable global operator new to require its parameter be exactly
__SIZE_TYPE__, so libcxxabi's operator new (declared with musl's size_t) is
rejected:
error: 'operator new' takes type size_t ('unsigned long') as 1st parameter
error: no overload of 'operator new[]' matching 'void *(*)(size_t)' (aka 'void *(*)(unsigned int)')
This is inert in C (the entire C userland — busybox, bash, coreutils — builds fine), so it stayed latent until the first C++ build on the target (bringing up libc++ for an on-target clang).
Reproduction
$ echo | wasmcc -dM -E -x c++ - | grep __SIZE_TYPE__
#define __SIZE_TYPE__ long unsigned int
$ printf '#include <stddef.h>\n_Static_assert(__builtin_types_compatible_p(size_t, unsigned long),"");\n' \
| wasmcc -c -x c -o /dev/null -
error: static assertion failed ... (size_t is 'unsigned int', not 'unsigned long')
Building LLVM_ENABLE_RUNTIMES=libcxx;libcxxabi;libunwind for wasm32-hwjs fails
on libcxxabi/src/stdlib_new_delete.cpp and cxa_vector.cpp with the errors above.
Proposed fix
Set _Addr = long in arch/wasm32/bits/alltypes.h.in so size_t (and the other
_Addr-based types: ptrdiff_t, ssize_t, intptr_t, …) is unsigned long,
matching the compiler's __SIZE_TYPE__ and the wasm32 ABI convention (upstream
LLVM / wasi-libc use unsigned long for size_t on wasm32). Byte-compatible on
wasm32 (int == long == 32-bit) — only the type identity changes, so the C ABI
and the prebuilt C userland are unaffected.
Confirmed end-to-end: regenerating bits/alltypes.h from the patched .in
via musl's own mkalltypes.sed yields size_t = unsigned long, and with that
header libc++ / libc++abi / libunwind build cleanly for wasm32-hwjs
(previously blocked at operator new).
Branch: fix/wasm32-size_t-addr-long Commit: 1a12e2b
--- a/arch/wasm32/bits/alltypes.h.in
+++ b/arch/wasm32/bits/alltypes.h.in
@@ -1,4 +1,4 @@
-#define _Addr int
+#define _Addr long
#define _Int64 long long
#define _Reg int
Proposed fix targets brintos/musl only — no distro submodule pins moved. All
distros share one lineage, so pin bumps are coordinated on merge, not per-engineer.
