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Prevent overflow of length bits for embedded structs

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Embedded structs only use 7 bits for the length, so it will overflow if
the GC can allocate large slots. We need to add the cap to struct_alloc.
This commit is contained in:
Peter Zhu 2026-07-10 20:22:19 +09:00
parent f132ecd1d9
commit 916d8c1050
Notes: git 2026-07-11 06:21:28 +00:00 
Merged: https://github.com/ruby/ruby/pull/17783
1 changed files with 3 additions and 1 deletions
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4
struct.c
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@ -829,7 +829,9 @@ struct_alloc(VALUE klass)
VALUE flags = T_STRUCT;
if (n > 0 && rb_gc_size_allocatable_p(embedded_size)) {
const long embed_len_max = RSTRUCT_EMBED_LEN_MASK >> RSTRUCT_EMBED_LEN_SHIFT;
if (n > 0 && n <= embed_len_max && rb_gc_size_allocatable_p(embedded_size)) {
flags |= n << RSTRUCT_EMBED_LEN_SHIFT;
if (RCLASS_MAX_IV_COUNT(klass) == 0) {
// We set the flag before calling `NEWOBJ_OF` in case a NEWOBJ tracepoint does