| Summary: | Warn for expanding range of an arithmetic type | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Matthew Wilcox <matthew> |
| Component: | c | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | UNCONFIRMED --- | ||
| Severity: | normal | Keywords: | diagnostic |
| Priority: | P3 | ||
| Version: | 11.0 | ||
| Target Milestone: | --- | ||
| Host: | Target: | ||
| Build: | Known to work: | ||
| Known to fail: | Last reconfirmed: | ||
I've just fixed multiple instances of bugs that look a lot like function f() when they should have been function g(). This affects filesystems in Linux which have to remember to cast an unsigned long to an off_t before shifting (or there will be a bug on 32-bit kernels when dealing with files that are larger than 4GB). When I looked for a warning option to add, I thought -Warith-conversions might do the job, but it doesn't. Maybe this functionality should be added there, or maybe it should have its own warning. I think what we're looking for is an operation which expands the range of the type (left shift, multiplication, addition; maybe subtraction?) and the rules of C require the operation to be done in a narrower type, but the result is assigned to a wider type. unsigned long long f(unsigned int i) { return i * 4096; } unsigned long long g(unsigned int i) { return i * 4096ULL; }