Re: [ALACPP] Why won't g++ tell me I'm dumb?

["Jon Stewart" <stew1@xxxxxxxxxxx>]

> void strrevtest() {
>    char* t;
>    t = ""; strrev(t);BOOST_CHECK_EQUAL( std::strcmp(t,""), 0);
>    t = "a"; strrev(t);BOOST_CHECK_EQUAL( std::strcmp(t,"a"), 0);
>    t = "ab"; strrev(t);BOOST_CHECK_EQUAL( std::strcmp(t,"ba"), 0);
>    t = "asdf"; strrev(t);BOOST_CHECK_EQUAL( std::strcmp(t,"fdsa"), 0);
>    t = "asdfg"; strrev(t);BOOST_CHECK_EQUAL( std::strcmp(t,"gfdsa"), 0);
> }
> 
> test_suite*
> init_unit_test_suite ( int argc, char** argv) {
>    test_suite* test = BOOST_TEST_SUITE( "strrev test");
>    test->add( BOOST_TEST_CASE( &strrevtest ));
>    return test;
> }
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> This produces a memory access violation when it does the first swap.  
> The reason is that I'm dumb and I was trying to modify a (const) string 
> literal.  Now, I can fix my test case by sticking in some strdup's, but 
> there was also a consensus that the C++ compiler ought to complain.  
> However, it really seems to just silently discard the const-ness, 
> despite the suggestions of the g++ man page.
> 
> Chris and I also tried with the Intel compiler, but that didn't 
> complain either.
> 
> So, is there some flag we're missing that would spit out a warning 
> about this const issue?


This is all supposition... I don't have my copy of Stroustrup at home...

Now that I look at this some more, it's simply another C gotcha'. To 
maintain backwarks compatibility with C, C++ would certainly need to allow 
you to assign a string literal to a char*. If you'd assigned the string 
literals to const char*'s, the compiler would bitch when you assigned a 
const type to a non-const type in the function call. But, I think C++ 
would have to allow this:

char *string = "I'm in write-only memory! Hahahaha!"; // ah, chardonnay

Were you using any optimization levels? One would think that could be 
allowed to edit string literals, but I'm pretty rusty on my C. Josh?



Jon
-- 
Jon Stewart                                 Advanced Los Angeles C++
stew1@xxxxxxxxxxx                           http://www.alacpp.org
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