Some programming mistakes

[bearophile]

An article, "Eight C++ programming mistakes the compiler won't 
catch":
http://pixelstech.net/article/index.php?id=1333893320

Its Reddit thread:
http://www.reddit.com/r/cpp/comments/s0o99/eight_c_programming_mistakes_the_compiler_wont/


Some quotations from the article, valid for D too:

> 2) Integer division
> 
> Many new programmers attempt to do the following:
> 
> int nX = 7;
> int nY = 2;
> float fValue = nX / nY;  // fValue = 3 (not 3.5!)
> 
> The underlying assumption here is that nX / nY will result in a
> floating point division because the result is being assigned to
> a floating point value. However, this is not the case.

GCC with -Wconversion finds that problem, but maybe with too much 
noise:

int main() {
     float fX = 7.0;
     int nY = 2;
     float fValue = fX / nY;
     return 0;
}

...>gcc -Wconversion test.c -o test
test.c: In function 'main':
test.c:4:5: warning: conversion to 'float' from 'int' may alter 
its value [-Wconversion]



> 4) Mixing signed and unsigned values
> 
> int nX;
> unsigned int nY;
> 
> if (nX - nY < 0)
>     // do something

GCC with -Wconversion finds it.
There are more interesting cases with mixing short with uint, etc.



> 6) Side effects in compound expressions or function calls
> 
> int foo(int x)
> {
> return x;
> }
> 
> int main()
> {
>     int x = 5;
>     std::cout << foo(x) * foo(++x);
> }
> 
> A good rule of thumb is to put any operator that
> causes a side effect in it’s own statement.

Bye,
bearophile