When you compile the file, the compiler invokes the linker which tries to generate an executable. But it cannot because you didn’t provide a function named main which is the function that will be executed when your program is launched. Either you don’t want to run the linker because you want to compile several files … Read more
GCC as of 4.9 has colourized output ☺ Append the following to your bashrc/zshrc/whatever. export GCC_COLORS=’error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01′
Turns out there isn’t a way to reliably recover the semaphore. Sure, anyone can post_sem() to the named semaphore to get the count to increase past zero again, but how to tell when such a recovery is needed? The API provided is too limited and doesn’t indicate in any way when this has happened. Beware … Read more
reinterpret_cast, static_cast, dynamic_cast and const_cast are the c++ cast alternatives. const_cast to remove const/volatile from a const variable. dynamic_cast to perform runtime validity checks when casting in between polymorphic types static_cast to perform e.g up/down-cast in a inheritance hierarchy, but with no runtime checks, or to explicitly perform conversions that could be implicit (e.g. float … Read more
This is actually a well-formed program that has two equally valid execution paths, so both compilers are right. a[1] = a.size() In this expression, the evaluation of the two operands of = are unsequenced. §1.9/15 [intro.execution] Except where noted, evaluations of operands of individual operators and of subexpressions of individual expressions are unsequenced. However, function … Read more
The typename is required by the standard. Template compilation requires a two step verification. During the first pass the compiler must verify the template syntax without actually supplying the type substitutions. In this step, std::map::iterator is assumed to be a value. If it does denote a type, the typename keyword is required. Why is this … Read more
You can simply use g++ to compile an empty function with the signature you require and extract the name from that. For example: echo “int f1(char *, int) {} ” | g++ -x c++ -S – -o- | grep “^_.*:$” | sed -e ‘s/:$//’ gives output _Z2f1Pci which is I think what you require. Make … Read more
The restrict keyword does a difference. I’ve seen improvements of factor 2 and more in some situations (image processing). Most of the time the difference is not that large though. About 10%. Here is a little example that illustrate the difference. I’ve written a very basic 4×4 vector * matrix transform as a test. Note … Read more
The error is because your gcc-core package and gcc-g++ are not of the same version. Either downgrade one of them to solve the problem or update both the libraries. Updating both the libraries is the recommended way.
teststruct defines a scope in C++. You can form the qualified id teststruct::u64. So the language rules for name lookup account for that, allowing members of classes and unions to hide identifiers in outer scope. Once u64 u64; is introduced, the unqualified u64 cannot refer to the global ::u64, only the member. And the member … Read more