[Clang-Tidy] readability-use-std-min-max should consider `std::clamp`

[SunBlack]

Tried the new check readability-use-std-min-max of the upcoming Clang-Tidy 19.

In one case we had following code:

if (ratio < 0.0F)
{
	ratio = 0.0F;
}
if (ratio > 1.0F)
{
	ratio = 1.0F;
}

Running run-clang-tidy-19 -header-filter='.*' -checks='-*,readability-use-std-min-max' -fix results in:

ratio = std::max(ratio, 0.0F);
ratio = std::min(ratio, 1.0F);

But in this case it would be better

ratio = std::clamp(ratio, 0.0F, 1.0F);

I don't know how complex it would be to recognize this pattern, i.e. whether it is better to introduce a readability-use-std-clamp, even if this may require a second pass, or whether this can be combined by changing the check to readability-use-std-min-max-clamp.

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: SunBlack (SunBlack)

Tried the new check `readability-use-std-min-max` of the upcoming Clang-Tidy 19.

In one case we had following code:

if (ratio < 0.0F)
{
	ratio = 0.0F;
}
if (ratio > 1.0F)
{
	ratio = 1.0F;
}

Running run-clang-tidy-19 -header-filter='.*' -checks='-*,readability-use-std-min-max' -fix results in:

ratio = std::max(ratio, 0.0F);
ratio = std::min(ratio, 1.0F);

But in this case it would be better

ratio = std::clamp(ratio, 0.0F, 1.0F);

I don't know how complex it would be to recognize this pattern, i.e. whether it is better to introduce a readability-use-std-clamp, even if this may require a second pass, or whether this can be combined by changing the check to readability-use-std-min-max-clamp.

[mathstuf]

Related (on the detection side) is the pattern of:

out = std::max(in[0], out);
out = std::max(in[1], out);
out = std::max(in[2], out);

which could be:

out = std::max({ in[0], in[1], in[2] });

[sparr]

I would also like to see this check suggest replacing a = std::min( b, std::max( c, a ) ) (and other similar constructions) with a = std::clamp( a, c, b )

[EugeneZelenko]

I would also like to see this check suggest replacing a = std::min( b, std::max( c, a ) ) (and other similar constructions) with a = std::clamp( a, c, b )

It'll be great! Just noticed similar pattern in my work code base yesterday.

[sparr]

Note that std::min( a, std::max( b, c ) ) without an assignment or other reference to one of the three variables (e.g. passing the result to a function) can't be simplified, because we don't know which of b or c is the value being clamped and which is the lower bound.

[carlosgalvezp]

Related (on the detection side) is the pattern of:

out = std::max(in[0], out);
out = std::max(in[1], out);
out = std::max(in[2], out);
which could be:

out = std::max({ in[0], in[1], in[2] });

This is already solved by modernize-min-max-use-initializer-list

[SunBlack]

@carlosgalvezp This issue wasn't about initializer list variant. It was about using std::clamp

[carlosgalvezp]

@carlosgalvezp This issue wasn't about initializer list variant. It was about using std::clamp

Yes sorry, I must have missclicked on the phone, the issue is relevant.

[carlosgalvezp]

For std::clamp we probably could have a modernize-use-std-clamp.