assertpp.hh

/* This header file defines a macro that works the same way as assert()
 * from assert.h, except that it also allows specifying expressions
 * whose values will be output alongside the failed assertion.
 * Error messages will be output to std::cerr
 * and the program terminated with std::terminate().
 *
 * Usage:
 *   assertpp(condition, [<expression> [...]]);
 *
 * Examples:
 *   assertpp(x<4);
 *   assertpp(x==4,  x);
 *   assertpp(vec.size() < limit,  limit, vec.size());
 *   assertpp(var1==var2,  var1, var2);
 *
 * Copyright: (C) 2015 Joel Yliluoma, http://iki.fi/bisqwit/
 * License: Creative Commons Attribution (CC-BY 1.0, 2.0 or 3.0)
 */

#include <iostream>
#include <exception>

#ifdef NDEBUG
  #define assertpp(condition, args...)
#else
template<typename...>
class assertpphandler
{
    const char* v;
public:
    assertpphandler(const char condstr[], const char file[], unsigned line, const char func[], const char* vars) : v(vars)
    {
        std::cerr << file << ':' << line << ": " << func << ": Assertion failed: " << condstr << " (";
        if(*v) std::cerr << "With ";
    }
    void operator() () { std::cerr << ")\n"; std::terminate(); }
    template<typename T, typename...U> void operator()(T&& v, U&&... rest)
    {
        GetVar() << std::forward<T>(v);
        (*this)(std::forward<U>(rest)...);
    }
private:
    std::ostream& GetVar()
    {
        int parens=0;
        if(*v == ',') { std::cerr << ", "; ++v; }
        while(*v == ' ' || *v == '\t' || *v == '\n' || *v == '\r' || *v == '\v') ++v;
        while(*v && (*v != ',' || parens != 0))
        {
            if(*v == '(') ++parens; else if(*v == ')') --parens;
            std::cerr << *v++;
        }
        return std::cerr << " = ";
    }
};

#ifdef __GNUC__
# define assertpp(condition, ...) do { \
    if(__builtin_expect(!(condition),false)) \
        assertpphandler<>(#condition, __FILE__, __LINE__, __PRETTY_FUNCTION__, #__VA_ARGS__)(__VA_ARGS__); } while(0)
#else
# define assertpp(condition, ...) do { \
    if(!(condition)) \
        assertpphandler<>(#condition, __FILE__, __LINE__, __func__, #__VA_ARGS__)(__VA_ARGS__); } while(0)
#endif

#endif