Re: "might be used uninitialized..." what?

From:

Victor Bazarov <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Sat, 29 Aug 2009 09:11:45 -0400

Message-ID:

<h7b9ek$8s9$1@news.datemas.de>

Alf P. Steinbach wrote:

It's possible that I'm blind on both eyes.

After all, it's late in the day (or morning) for me.

But, I have this code which adds a string to a list of strings:

    virtual cppx::Index add(
        cppx::WideString const& s, cppx::WideString const& data
        )
    {
        int const id = myStrings.add( data );

        try
        {
            return Base::basicAdd( s, id );
        }
        catch( ... )
        {
            myStrings.remove( id );
            throw;
        }
    }

Compiling with g++ 3.4.5, options (copy/paste from the IDE's build log)

  -Wall -O -pedantic -Wall -g -O -pedantic -Wall -std=c++98
-Wno-long-long -Wwrite-strings

the compiler complains that

    warning: 'id' might be used uninitialized in this function

Which line?

And why do use such an old compiler, don't they already have v4.x? Of
course, I can be mistaken, you've only posted a fragment, but 4.2 does
not produce any errors in this:

#include <string>

unsigned foo(std::string& s)
{
    const int id = s.append(" ").size();
    try
    {
        return s.size();
    }
    catch(...)
    {
        return id;
    }
}

(except about the missing 'main').

Now, I've tried to *reproduce* the warning, with the following code:

    int add(); // { return 666; }
    void remove( int ); // {}
    int foo( int ); // {}

    struct S
    {
        virtual int bar()
        {
            int const id = add();
            try
            {
                return foo( id );
            }
            catch( ... )
            {
                remove( id );
                throw;
            }
        }
    };

    int main()
    {
        S().bar();
    }

But this code does not produce the warning.

What is it that the compiler sees that I don't see?

<shrug> How do you know somebody else's hallucinations?

V
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