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Fix alignment issue in md_mark_store_ptr() #290

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Fix alignment issue in md_mark_store_ptr() #290

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e55e9c9
Fix alignment issue in md_mark_store_ptr()
wmww Jul 20, 2025
549cefe
Change union portion of MD_MARK_tag to just beg and end
wmww Jul 21, 2025
664a772
Simplify mark pointers more
wmww Jul 21, 2025
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27 changes: 12 additions & 15 deletions src/md4c.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2520,8 +2520,13 @@ md_free_ref_defs(MD_CTX* ctx)
* cache line.)
*/
struct MD_MARK_tag {
OFF beg;
OFF end;
union {
struct {
OFF beg;
OFF end;
};
void* pointer; // Dummy marks can sometimes store a pointer
};

/* For unresolved openers, 'next' may be used to form a stack of
* unresolved open openers.
Expand Down Expand Up @@ -2653,28 +2658,20 @@ md_mark_stack_pop(MD_CTX* ctx, MD_MARKSTACK* stack)
return top;
}

/* Sometimes, we need to store a pointer into the mark. It is quite rare
* so we do not bother to make MD_MARK use union, and it can only happen
/* Sometimes, we need to store a pointer into the mark. It can only happen
* for dummy marks. */
static inline void
md_mark_store_ptr(MD_CTX* ctx, int mark_index, void* ptr)
{
MD_MARK* mark = &ctx->marks[mark_index];
MD_ASSERT(mark->ch == 'D');

/* Check only members beg and end are misused for this. */
MD_ASSERT(sizeof(void*) <= 2 * sizeof(OFF));
memcpy(mark, &ptr, sizeof(void*));
MD_ASSERT(ctx->marks[mark_index].ch == 'D');
ctx->marks[mark_index].pointer = ptr;
}

static inline void*
md_mark_get_ptr(MD_CTX* ctx, int mark_index)
{
void* ptr;
MD_MARK* mark = &ctx->marks[mark_index];
MD_ASSERT(mark->ch == 'D');
memcpy(&ptr, mark, sizeof(void*));
return ptr;
MD_ASSERT(ctx->marks[mark_index].ch == 'D');
return ctx->marks[mark_index].pointer;
}

static inline void
Expand Down