| author |  Carl Åstholm <carl@astholm.se> 2025-11-07 22:15:30+01:00 |
| committer |  Andrew Kelley <andrew@ziglang.org> 2026-01-02 16:55:11-08:00 |
| log | c9fa8e46df21cdf66b291fb3dfdcef1b6a1d3cab |
| tree | be1ef792bffa9d7f6eb6fa186d9100d31181a8db |
| parent | 1bf29757d963b301c1fcfccb9b39b277381de115 |
Use `mmap` `std.heap.page_allocator` impl when compiling for Wasm + libc
When linking libc, it should be the libc that manages the heap. The main
Wasm memory might have been configured as non-growable, which makes
`WasmAllocator` a poor default and causes the common `DebugAllocator`
use case fail with OOM errors unless the user uses `std_options` to
override the default page allocator. Additionally, on Emscripten,
growing Wasm memory without notifying the JS glue code will cause array
buffers to get detached and lead to spurious crashes.3 files changed, 14 insertions(+), 12 deletions(-)
lib
lib/std/c.zig+13-2
| ... | ... | @@ -1885,7 +1885,16 @@ pub const POLL = switch (native_os) { |
| 1885 | 1885 | /// Basic memory protection flags |
| 1886 | 1886 | pub const PROT = switch (native_os) { |
| 1887 | 1887 | .linux => linux.PROT, |
| 1888 | .emscripten => emscripten.PROT, | |
| 1888 | // https://github.com/emscripten-core/emscripten/blob/08e2de1031913e4ba7963b1c56f35f036a7d4d56/system/lib/libc/musl/include/sys/mman.h#L57-L62 | |
| 1889 | // lib/libc/include/wasm-wasi-musl/sys/mman.h | |
| 1890 | .emscripten, .wasi => struct { | |
| 1891 | pub const NONE = 0; | |
| 1892 | pub const READ = 1; | |
| 1893 | pub const WRITE = 2; | |
| 1894 | pub const EXEC = 4; | |
| 1895 | pub const GROWSDOWN = 0x01000000; | |
| 1896 | pub const GROWSUP = 0x02000000; | |
| 1897 | }, | |
| 1889 | 1898 | // https://github.com/SerenityOS/serenity/blob/6d59d4d3d9e76e39112842ec487840828f1c9bfe/Kernel/API/POSIX/sys/mman.h#L28-L31 |
| 1890 | 1899 | .openbsd, .haiku, .dragonfly, .netbsd, .illumos, .freebsd, .windows, .serenity => struct { |
| 1891 | 1900 | /// page can not be accessed |
| ... | ... | @@ -8640,7 +8649,9 @@ pub const O = switch (native_os) { |
| 8640 | 8649 | |
| 8641 | 8650 | pub const MAP = switch (native_os) { |
| 8642 | 8651 | .linux => linux.MAP, |
| 8643 | .emscripten => packed struct(u32) { | |
| 8652 | // https://github.com/emscripten-core/emscripten/blob/08e2de1031913e4ba7963b1c56f35f036a7d4d56/system/lib/libc/musl/include/sys/mman.h#L21-L39 | |
| 8653 | // lib/libc/include/wasm-wasi-musl/sys/mman.h | |
| 8654 | .emscripten, .wasi => packed struct(u32) { | |
| 8644 | 8655 | TYPE: enum(u4) { |
| 8645 | 8656 | SHARED = 0x01, |
| 8646 | 8657 | PRIVATE = 0x02, |
lib/std/heap.zig+1-1
| ... | ... | @@ -352,7 +352,7 @@ pub const page_allocator: Allocator = if (@hasDecl(root, "os") and |
| 352 | 352 | @hasDecl(root.os, "heap") and |
| 353 | 353 | @hasDecl(root.os.heap, "page_allocator")) |
| 354 | 354 | root.os.heap.page_allocator |
| 355 | else if (builtin.target.cpu.arch.isWasm()) .{ | |
| 355 | else if (builtin.target.cpu.arch.isWasm() and !builtin.link_libc) .{ | |
| 356 | 356 | .ptr = undefined, |
| 357 | 357 | .vtable = &WasmAllocator.vtable, |
| 358 | 358 | } else if (builtin.target.os.tag == .plan9) .{ |
lib/std/os/emscripten.zig-9
| ... | ... | @@ -331,15 +331,6 @@ pub const POLL = struct { |
| 331 | 331 | pub const RDBAND = 0x080; |
| 332 | 332 | }; |
| 333 | 333 | |
| 334 | pub const PROT = struct { | |
| 335 | pub const NONE = 0x0; | |
| 336 | pub const READ = 0x1; | |
| 337 | pub const WRITE = 0x2; | |
| 338 | pub const EXEC = 0x4; | |
| 339 | pub const GROWSDOWN = 0x01000000; | |
| 340 | pub const GROWSUP = 0x02000000; | |
| 341 | }; | |
| 342 | ||
| 343 | 334 | pub const rlim_t = u64; |
| 344 | 335 | |
| 345 | 336 | pub const RLIM = struct { |