https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66170
Bug ID: 66170
Summary: Bogus warning with -Wsign-conversion when using
static_cast<size_t> on an int
Product: gcc
Version: 4.9.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: yaghmour.shafik at gmail dot com
Target Milestone: ---
Given the following code:
#include <cstring>
int main()
{
int length = 0;
size_t n;
n = static_cast<size_t>(length) ; // Line 8
n = static_cast<size_t>(length) * sizeof(int) ;
n = sizeof(int) * static_cast<long unsigned int>(length) ;
n = sizeof(int) * static_cast<unsigned int>(length) ; // Line 11
n = sizeof(int) * static_cast<size_t>(length) ; // Line 13
}
building with gcc 4.9.2 or greater using the following command line:
g++ -Wsign-conversion
generates the following warning on line 13:
warning: conversion to 'long unsigned int' from 'int' may change the sign of
the result [-Wsign-conversion]
This looks like an error to me, the documentation for -Wsign-conversion says:
An explicit cast silences the warning
and line 8 to line 11 are very similar but do not generate any warning.
Optimization level does not make a difference and -Wall -Wextra does not
indicate additional issues.
