https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87129
Bug ID: 87129
Summary: -Wsign-conversion Erroneously Triggered When
Dereferencing Pointer From Implicit User Conversion
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: ian at geometrian dot com
Target Milestone: ---
When dereferencing a pointer created from calling an implicit user conversion,
g++ erroneously produces a warning from -Wsign-conversion about (inexplicably)
converting `size_t` into a signed integer type. If a pointer of the same type
is used instead, (correctly) no warning is generated.
Minimal sample:
//Compile with `-Wsign-conversion`
#include <cstdlib> //`size_t`
extern float* data;
struct Accessor {
operator float*() {
return data;
}
};
float foo(Accessor accessor, size_t i) {
return accessor[i];
}
Output (9.0.0 20180824 x86-64):
<source>: In function 'float foo(Accessor, size_t)':
<source>:13:20: warning: conversion to 'long int' from 'size_t' {aka 'long
unsigned int'} may change the sign of the result [-Wsign-conversion]
13 | return accessor[i];
| ^
Tested as occurring in many versions of g++, from 9.0 back to at least 4.4.
