CODEWITHSUNDEEP
c++gcctype-conversioncompiler-warningssuppress-warnings
Jacko
Jacko

Reputation: 13195

Trying to fix conversion warning

I am getting the following error:

warning: conversion to ‘short unsigned int’ from ‘int’ may alter its value [-Wconversion]

for the method

template<typename T> bool get_int(FILE* IN, T* val) {
    T rc = 0;
    for (size_t i = 0; i < sizeof(T) << 3; i += 8) {
        int temp = getc(IN);
        if (temp == EOF)
            return false;
        rc |= (T)temp << i;
    }
    *val = rc;
    return true;
}

when I have the lines

unsigned short foo;
get_int<unsigned short>(IN, &foo);

How can I get rid of this GCC warning?

Upvotes: 0

Views: 250

Answers (2)

ssbssa
ssbssa

Reputation: 1226

Try this:

rc |= (T)(temp << i);

(T)temp is promoted to int again for the bitwise shift.

Upvotes: 1

Barry
Barry

Reputation: 302987

Don't reinvent the wheel. There's already a function to read multiple bytes of binary data: fread():

template<typename T>
bool get_int(FILE* f, T* val) {
    return fread(val, sizeof(T), 1, f) == sizeof(T);
}

Note that you don't have to explicitly specify the types when calling function templates - you can let deduction to its thing:

unsigned short foo;
get_int(IN, &foo);

Upvotes: 1

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