Assert callable arg count matches buffer dims in for_each_element#9214
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abadams wants to merge 3 commits into
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Assert callable arg count matches buffer dims in for_each_element#9214abadams wants to merge 3 commits into
abadams wants to merge 3 commits into
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Buffer::for_each_element previously accepted a callable taking fewer int
arguments than the buffer's dimensionality, silently iterating only over a
reduced-dimensionality slice. A nullary callable (e.g. buffer.fill(rng))
therefore wrote only the origin element. This is an easy mistake to make and
produces no error.
Require the callable to take either a const int *, or exactly as many int
arguments as the buffer has dimensions. This uncovered three real bugs where
buffers were only ever having their first element randomized:
- test/fuzz/lossless_cast.cpp: buf.fill(fuzz)
- test/correctness/interleave_rgb.cpp: fill([]() { return rand(); })
- test/correctness/multiple_scatter.cpp: fill(std::mt19937{0})
All three are fixed to use for_each_value, which passes an element reference
and does not depend on coordinates. The reduced-slice usage in
test/correctness/for_each_element.cpp is rewritten to slice off a channel
first so the callable's arg count matches the iteration domain.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A zero-argument callable passed to fill (for example a random number generator) has no coordinate to consume, so there is no distinction between filling via for_each_element and for_each_value. Dispatch such callables to for_each_value, which evaluates the callable once per element. This makes the natural buffer.fill(rng) idiom fill the whole buffer instead of tripping the for_each_element arg-count assertion. With this, the previously-broken buffer initializations in interleave_rgb, multiple_scatter, and lossless_cast (which only ever randomized the origin element) are fixed by reverting them to their original fill(rng) form. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The for_each_element arg-count assertion rejects a callable taking fewer int arguments than the buffer's dimensionality. These calls iterated a 2D domain over a 3D buffer and handled all channels inside the callable, so slice off the channel dimension first to get a matching 2D domain. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Buffer::for_each_element previously accepted a callable taking fewer int arguments than the buffer's dimensionality, silently iterating only over a reduced-dimensionality slice. Buffer::fill uses Buffer::for_each_element. A nullary callable (e.g. buffer.fill(rng)) therefore wrote only the origin element. This is an easy mistake to make and produces no error.
This PR requires a callable passed to for_each_element to take either a const int *, or exactly as many int arguments as the buffer has dimensions. This uncovered three real bugs where buffers were only ever having their first element randomized:
Buffer::fill was changed to defer to for_each_value when passed a zero-arg callable. This is unambiguous, because it behaves in exactly the same way as if it deferred to for_each_element for scalar buffers. The reduced-slice usage in test/correctness/for_each_element.cpp is rewritten to slice off a channel first so the callable's arg count matches the iteration domain.
This is a breaking change. It will cause user code that uses this iterate-over-a-slice feature to assert-fail. I give 50/50 odds whether such user code is working as intended, so I think this is worth it. It may also break user code that is relying on fill(rng) to only initialize the first element, but surely such code is buggy.