Assert with dynamic message?

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assert
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assert not declared

In my program I want to use asserts that show an error message. Apart from the well known workarounds for C and C++ there's the "real" solution as BOOST offers BOOST_ASSERT_MSG( expr, msg ) (see also assert() with message)

But a static message isn't enough for me, I also want to show sometimes the failed variables, e.g. in a case like

BOOST_ASSERT_MSG( length >= 0, "No positive length found! It is " << length )

As you can see I'd like to format the message "string" as an stringstream or ostream as that'd allow me to easily show custom types (assuming I've defined the relevant formating function).

The problem here is that BOOST_ASSERT_MSG is by default requiring a char const * so that's not compatible.

Is there a way to redefine / overload assertion_failed_msg() in such a way that using a stream as message will work? How? (My naive approach failed as the compiler first wanted to do an operator<<("foo",bar) on the message itself...)

You could define your own macro

#define ASSERT_WITH_MSG(cond, msg) do \
{ if (!(cond)) { std::ostringstream str; str << msg; std::cerr << str.str(); std::abort(); } \
} while(0)

assert, Dynamic memory management There is no standardized interface to add an additional message to assert errors. A portable way to include� I'm looking for a way to add custom messages to assert statements. I found this questions Add custom messages in assert? but the message is static there. I want to do something like this: assert((0 < x) && (x < 10), std::string("x was ") + myToString(x));

It's relatively trivial to achieve this.

BOOST_ASSERT_MSG( length >= 0, (std::stringstream() << "No positive length found! It is " << length).str().c_str() )

7.12a — Assert and static_assert, An assert statement is a preprocessor macro that evaluates a This error message contains the conditional expression that failed, along with @assert is a compile-time macro, it's text content cannot be dynamically created. The expression assert(E) is guaranteed to be a constant subexpression, if either NDEBUG is defined at the point where assert is last defined or redefined (i.e., where the header <cassert> or <assert.h> was last included); or E, contextually converted to bool, is a constant subexpression that evaluates to true. (since C++17)

I use the BOOST_ASSERT_MSG with my own wrapper around it, so that specifying the assert message with multiple operator<< seems less complex.

#if defined ASSERT_ENABLED 

    #define ASSERT(cond, msg) {\
        if(!(cond))\
        {\
            std::stringstream str;\
            str << msg;\
            BOOST_ASSERT_MSG(cond, str.str().c_str());\
        }\
    }
#else
    #define ASSERT(...) 
#endif

usage example, provide custom message like you are outputting to cout:

  ASSERT(execSize == (_oldSize - remaining), "execSize : " << execSize << ", _oldSize : " << _oldSize << ", remaining : " << remaining);

What it does is, if ASSERT_ENABLED is defined,enable the assertion messages. if(!(cond)) part is optimization, which avoids the costly string operations specified by macro parameter msg, if cond is true

Chapter 4. Interpolating constraint error messages, Message interpolation is the process of creating error messages for violated constraint violations with the messages shown by the assertions in Example 4.3, use an EL expression with a ternery expression to dynamically chose singular or� M_Assert(ptr != nullptr, "MyFunction: requires non-null argument"); And in case of failure you will get a message like this: Assert failed: MyFunction: requires non-null argument. Expected: ptr != nullptr. Source: C:\MyProject\src.cpp, line 22. Nice and clean, feel free to use it in your code =)

Here is a solution that doesn't rely on macros. Instead, it uses a tiny bit of templating and lambda syntax.

template<typename Fn> 
void assert_fn( bool expr, Fn fn) {
  if (!expr) {
    fn();
    abort();
  }
}

The argument fn can be any callable. For instance you can call it like so:

assert_fn( a==b, [&](){ cout << "Assertion failed: a="<< a << 
                                " is different from but b=" << b << endl; } ); 

The advantage is that the output is that you are not calling abort explicitly and the output is fully customizable. The this advantage, of course, are the seven extra characters of lambda function boilerplate: [&](){} )

Assertions, System.assert(myStr == 'something else', 'Assertion Failed Message');. Asserts that assert(meaning == 42, "Dynamic type conversion failed") assert statement takes an expression and optional message. assert statement is used to check types, values of argument and the output of the function.

If you are working on Windows only, you can take a look to assert macro. Under the hood it uses _wassert. You can write your own assert macro using it. For instance in my case if I get some point, I want to show assert without conditions:

#ifdef DEBUG
    const std::wstring assert_msg = /* build the string here */;
    _wassert(assert_msg.c_str(), _CRT_WIDE(__FILE__), (unsigned)(__LINE__));
#endif

I think on other OS you can do the same trick, just take look at assert macro.

js.node.Assert - HXNODEJS, The assert module provides a set of assertion functions for verifying invariants. staticdoesNotThrow(fn:() ‑> Void, ?error:Class<Dynamic>, ?message:String):� Assert.Throws(Is.TypeOf<InvalidOperationException>() .And.Message.EqualTo("Cannot read temperature before initializing."), () => sut.ReadCurrentTemperature()); There’s some personal preference involved when choosing a style, for example the preceding code could be considered more verbose by some and may muddle the distinction between the Act

Assertions in Python, An expression is tested, and if the result comes up false, an exception is raised. Assertions are carried out by the assert statement, the newest keyword to Python, � static_assert(sizeof(void *) == 4, "64-bit code generation is not supported."); Description. In the following example, the static_assert declaration has class scope. The static_assert verifies that a template parameter is a plain old data (POD) type.

Understanding static_assert in C++ 11, Static assertions are a way to check if a condition is true when the code is compiled. If it isn't, the compiler is required to issue an error message� A Computer Science portal for geeks. It contains well written, well thought and well explained computer science and programming articles, quizzes and practice/competitive programming/company interview Questions.

Assertions in C/C++, For example, we may use assertion to check if pointer returned by malloc() is NULL or not. Following is syntax for assertion. void assert( int� NUnit Assert class is used to determine whether a particular test method gives expected result or not. In a test method, we write code the check the business object behavior. That business object returns a result. In Assert method we

Comments
  • Please see stackoverflow.com/questions/1067226/…
  • If you use while(0), omit the ;.
  • I hoped to do it that way, but the compiler complains: error: ‘struct std::basic_ostream<char>’ has no member named ‘str’
  • Oh, yeah. I keep forgetting how broken the stringstream lib is.
  • You have to static_cast<std::stringstream&>() the return value of operator<<() to be able to use std::stringstream::str(). Otherwise you're trying to call std::ostream::str(), which doesn't exist.
  • Do you really need #if defined ASSERT_ENABLED ? I think if assert is disabled, the statements are removed anyway, if using an optimising compiler. Am I correct?
  • @SohailSi: Yes, #if defined ASSERT_ENABLED is for optimization. Generally release builds are meant to be with assertions disabled. This removes code from the binary. Smaller binary, less code, better use of instruction cache. While assert saves lot of time in debugging. Sometimes, a simple assert check could save 3 days of debugging time.
  • I mean if defined ASSERT_ENABLED is false then the compiler should automatically remove the BOOST_ASSERT_MSG statements, hence should remove the rest of your assert code. So ASSERT_ENABLED is not necessary to be explicitly checked. But I am not sure why it is needed to be said explicitly. Where am I wrong?