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Remove the trick of pushing an extra N+1 entry to function_offsets. It's bug-prone.

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Brian Carroll 2022-11-17 07:43:26 +00:00
parent 0c81063c68
commit 24e6e8445d
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2 changed files with 24 additions and 20 deletions
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30
crates/wasm_module/src/sections.rs
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@ -1195,37 +1195,33 @@ impl<'a> CodeSection<'a> {
});
}
*cursor += 1;
let section_size = u32::parse((), module_bytes, cursor)?;
let section_size = u32::parse((), module_bytes, cursor)? as usize;
let section_body_start = *cursor;
let count = u32::parse((), module_bytes, cursor)?;
let function_bodies_start = *cursor;
let next_section_start = section_body_start + section_size as usize;
let function_count = u32::parse((), module_bytes, cursor)?;
let next_section_start = section_body_start + section_size;
// preloaded_bytes starts at the function count, since that's considered the zero offset in the linker data.
// But when we finally write to file, we'll exclude the function count and write our own, including app fns.
let mut preloaded_bytes =
Vec::with_capacity_in(next_section_start - function_bodies_start, arena);
preloaded_bytes.extend_from_slice(&module_bytes[section_body_start..*cursor]);
// `bytes` must include the function count for linker offsets to be correct.
let mut bytes = Vec::with_capacity_in(section_size + section_size / 2, arena);
bytes.extend_from_slice(&module_bytes[section_body_start..*cursor]);
let mut preloaded_offsets = Vec::with_capacity_in(count as usize, arena);
let mut function_offsets = Vec::with_capacity_in(function_count as usize, arena);
// While copying the code bytes, also note where each function starts & ends
// Later we will use this for dead code elimination
while *cursor < next_section_start {
let fn_start = *cursor;
preloaded_offsets.push((fn_start - section_body_start) as u32);
function_offsets.push((fn_start - section_body_start) as u32);
let fn_length = u32::parse((), module_bytes, cursor)? as usize;
*cursor += fn_length;
preloaded_bytes.extend_from_slice(&module_bytes[fn_start..*cursor]);
bytes.extend_from_slice(&module_bytes[fn_start..*cursor]);
}
preloaded_offsets.push((next_section_start - section_body_start) as u32);
debug_assert_eq!(preloaded_offsets.len(), 1 + count as usize);
debug_assert_eq!(function_offsets.len(), function_count as usize);
Ok(CodeSection {
function_count: count,
bytes: preloaded_bytes,
function_offsets: preloaded_offsets,
function_count,
bytes,
function_offsets,
dead_import_dummy_count: 0,
})
}