WIP: issue #241: range checking #242
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@tbeu something like this? |
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Yes, with setting |
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Please let me also know if UBSan is happy with this kind of fixes. |
| #include <stddef.h> | ||
| #include <stdint.h> |
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| #include <stdint.h> | |
| #include <limits.h> |
This fails if HAVE_STDINT_H is not defined. Did you mean to include limits.h instead?
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Oh. Doesn't matio require C99? stdint.h I believe is the correct header for UINT32_MAX and friends: https://en.cppreference.com/w/c/types/integer
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No, it's not C99. Go for https://en.cppreference.com/w/c/types/limits instead.
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No, it's not C99.
Oh. So I guess that's why you have mat_int32_t instead of just using int32_t?
Go for https://en.cppreference.com/w/c/types/limits instead.
UINT32_MAX is not there.
So I guess we need a custom MAT_UINT32_MAX somewhere...
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Or I just use literals like 4294967295U?
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You can see the safe-math.h where literals (in hex) are used.
src/read_data.c
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| TT min_ = (TT)READ_TYPE_MIN; \ | ||
| TT max_ = (TT)READ_TYPE_MAX; \ | ||
| const size_t block_size = READ_BLOCK_SIZE / data_size; \ | ||
| if ( len <= block_size ) { \ | ||
| readcount = fread(v, data_size, len, (FILE *)mat->fp); \ | ||
| if ( readcount == len ) { \ | ||
| for ( i = 0; i < len; i++ ) { \ | ||
| data[i] = (T)v[i]; \ | ||
| TT val_ = v[i]; \ | ||
| if (val_ >= min_ && val_ <= max_) { \ | ||
| data[i] = (T)val_; \ | ||
| } else { \ | ||
| break; \ | ||
| } \ |
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So I've just realized a problem... when this cast on line 57 is doing float -> int, let's say uint8_t specifically, the valid range of floats that can be legally cast to uint8_t are [-0.5, 255.5] (I forget if inclusive or exclusive), but READ_TYPE_MIN is 0 and READ_TYPE_MAX is 255, so we would in fact start rejecting some valid cases.
Not sure best way to do this...
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For integer conversion you can read http://tzimmermann.org/2018/04/20/safe-integer-conversion-in-c/.
For floating-point to integer conversion we need to deal with rounding. There is https://en.cppreference.com/w/c/numeric/math/round in C99, which rounds to nearest integer.
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For integer conversion you can read http://tzimmermann.org/2018/04/20/safe-integer-conversion-in-c/.
It's a nice write up, thanks for sharing. I'm familiar with these thing already though. Here's another nice write up you might like: https://www.frama-c.com/2013/05/02/Harder-than-it-looks-rounding-float-to-nearest-integer-part-1.html It's tricky stuff!
For floating-point to integer conversion we need to deal with rounding. There is https://en.cppreference.com/w/c/numeric/math/round in C99, which rounds to nearest integer.
The current behaviour in master (data[i] = (T)v[i];) does not round, it truncates. Do you want to change that?
But what I meant by "Not sure best way to do this" was more with regards to this codebase, not numeric conversions in C generally. The macros like READ_DATA maybe need to be split into 2 macros, one for integers and one for floats. Consider your suggestion of calling round: how can READ_DATA conditionally do that when it doesn't know if it's dealing with integers or floats? Maybe I'm missing some nice way... typeof might be handy, but that's new in C23...
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@tbeu want me to just take my best stab at it?
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I gave it a try, but have just realised what I've committed is rather wrong... will continue tomorrow.
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