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Assert the destination buffer size in get_bytes

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get_elements() only receives a raw pointer and cannot know the size of
its destination, so the destination-size guarantee is asserted at the
caller that owns the buffer: after resizing `result`, assert it has room
for `wanted` bytes at `old_size`. Together with the `copied <= wanted`
assert at the memcpy, this makes the "destination is large enough"
invariant explicit on both sides of the call.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Niels Lohmann
2026-07-04 14:28:40 +02:00
co-authored by Claude Opus 4.8
parent 79a8c279c0
commit 0c8ec0a2fc
2 changed files with 6 additions and 0 deletions
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single_include/nlohmann/json.hpp
+3
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@@ -13176,6 +13176,9 @@ class binary_reader
: chunk_size;
const std::size_t old_size = result.size();
result.resize(old_size + wanted);
// the destination now has room for `wanted` bytes at offset
// old_size, which is what get_elements() is allowed to write
JSON_ASSERT(result.size() >= old_size + wanted);
const std::size_t bytes_read = ia.get_elements(&result[old_size], wanted);
chars_read += bytes_read;
if (JSON_HEDLEY_UNLIKELY(bytes_read < wanted))