https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88566
Bug ID: 88566
Summary: -Wconversion not using value range information
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: hoganmeier at gmail dot com
Target Milestone: ---
https://godbolt.org/z/p0RMde
unsigned char foo(uint8_t pin)
{
if (pin >= 3 && pin <= 6) return pin - 2;
if (pin >= 9 && pin <= 10) return pin - 4;
if (pin >= 20 && pin <= 23) return pin - 13;
return 0;
}
$ gcc -O3 -Wconversion -S
<source>:5:39: warning: conversion from 'int' to 'uint8_t' {aka 'unsigned
char'} may change value [-Wconversion]
5 | if (pin >= 3 && pin <= 6) return pin - 2;
| ~~~~^~~
gcc should be aware that the value is well within the uint8_t range.
