Summary:
The bugprone-too-small-loop-variable check often catches loop variables which can represent "big enough" values, so we don't actually need to worry about that this variable will overflow in a loop when the code iterates through a container. For example a 32 bit signed integer type's maximum value is 2 147 483 647 and a container's size won't reach this maximum value in most of the cases.
So the idea of this option to allow the user to specify an upper limit (using magnitude bit of the integer type) to filter out those catches which are not interesting for the user, so he/she can focus on the more risky integer incompatibilities.
Next to the option I replaced the term "positive bits" to "magnitude bits" which seems a better naming both in the code and in the name of the new option.
Reviewers: JonasToth, alexfh, aaron.ballman, hokein
Reviewed By: JonasToth
Subscribers: Eugene.Zelenko, xazax.hun, jdoerfert, cfe-commits
Tags: #clang-tools-extra, #clang
Differential Revision: https://reviews.llvm.org/D59870
llvm-svn: 358356
The new checker searches for those for loops which has a loop variable with a "too small" type which means this type can't represent all values which are part of the iteration range.
For example:
```
int main() {
long size = 300000;
for( short int i = 0; i < size; ++i) {}
}
```
The short type leads to infinite loop here because it can't store all values in the `[0..size]` interval. In a real use case, size means a container's size which depends on the user input. Which means for small amount of objects the algorithm works, but with a larger user input the software will freeze.
The idea of the checker comes from the LibreOffice project, where the same check was implemented as a clang compiler plugin, called `LoopVarTooSmall` (LLVM licensed).
The idea is the same behind this check, but the code is different because of the different framework.
Patch by ztamas.
Reviewers: alexfh, hokein, aaron.ballman, JonasToth, xazax.hun, whisperity
Reviewed By: JonasToth, whisperity
Differential Revision: https://reviews.llvm.org/D53974
llvm-svn: 346665
Tamas Zolnai