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fix(libghostty): ensure memory is zeroed in runtime safety modes for wasm/freestanding (#11955)

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Zero page memory on freestanding/wasm where allocator reuses freed slots
without clearing. Allows recreating a new or multiple terminals.
This commit is contained in:
Mitchell Hashimoto
2026-03-29 06:40:09 -07:00
committed by GitHub
parent debcffbadb 420de124f0
commit 1c14b9615b
1 changed files with 10 additions and 6 deletions
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16
src/terminal/PageList.zig
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@@ -478,9 +478,12 @@ fn initPages(
page_alloc.free(page_buf);
// In runtime safety modes we have to memset because the Zig allocator
// interface will always memset to 0xAA for undefined. In non-safe modes
// we use a page allocator and the OS guarantees zeroed memory.
if (comptime std.debug.runtime_safety) @memset(page_buf, 0);
// interface will always memset to 0xAA for undefined. On freestanding
// (WASM), the WasmAllocator reuses freed slots without zeroing since
// only fresh memory.grow pages are guaranteed zero by the WASM spec.
// On native, the OS page allocator (mmap) returns zeroed pages.
if (comptime std.debug.runtime_safety or builtin.os.tag == .freestanding)
@memset(page_buf, 0);
// Initialize the first set of pages to contain our viewport so that
// the top of the first page is always the active area.
@@ -3385,9 +3388,10 @@ inline fn createPageExt(
else
page_alloc.free(page_buf);
// Required only with runtime safety because allocators initialize
// to undefined, 0xAA.
if (comptime std.debug.runtime_safety) @memset(page_buf, 0);
// In runtime safety modes, allocators fill with 0xAA. On freestanding
// (WASM), the WasmAllocator reuses freed slots without zeroing.
if (comptime std.debug.runtime_safety or builtin.os.tag == .freestanding)
@memset(page_buf, 0);
page.* = .{
.data = .initBuf(.init(page_buf), layout),