g++ – Page 6 – Tarik Billa

How to get around GCC ‘((void)& b +4)’ may be used uninitialized in this function warning while using boost::optional

August 30, 2023 by Tarik

There are two levels of uninitialized analysis in gcc: -Wuninitialized: flags variables that are certainly used uninitialized -Wmaybe-uninitialized: flags variables that are potentially used uninitialized In gcc (*), -Wall turns on both levels even though the latter has spurious warnings because the analysis is imperfect. Spurious warnings are a plague, so the simplest way to … Read more

Mixing C and C++ with CMAKE

August 30, 2023 by Tarik

The compiler and linker is usually determined by the file extension if not set otherwise. So as long as the file endings are fine, your code is compiled and linked with the correct compiler. On a side note, remember to make the correct extern C declarations, if you mix C and C++.

GNU C++ how to check when -std=c++0x is in effect?

August 26, 2023 by Tarik

There seems, with gcc 4.4.4, to be only one predefined macro hinting that -std=c++0x is in effect: #define __GXX_EXPERIMENTAL_CXX0X__ 1 I don’t have access to gcc 4.5.0 , but you can check that one yourself: [16:13:41 0 ~] $ g++ -E -dM -std=c++0x -x c++ /dev/null >b [16:13:44 0 ~] $ g++ -E -dM -std=c++98 … Read more

Should templated functions take lambda arguments by value or by rvalue reference?

August 25, 2023 by Tarik

FunctorT&& is a universal reference and can match anything, not only rvalues. It’s the preferred way to pass things in C++11 templates, unless you absolutely need copies, since it allows you to employ perfect forwarding. Access the value through std::forward<FunctorT>(f), which will make f an rvalue again if it was before, or else will leave … Read more

VSCode c++ task.json include path and libraries

August 24, 2023 by Tarik

1. Am I setting up VSCode correctly? Mostly. The fact that you have to specify the include paths twice (once in c_cpp_properties.json and again in a file that describes your build) is unavoidable. In VSCode, the build system and the editor do not understand each other, and both need this information. In contrast, with Visual … Read more

GCC error with variadic templates: “Sorry, unimplemented: cannot expand ‘Identifier…’ into a fixed-length argument list”

August 24, 2023 by Tarik

There is a trick to get this to work with gcc. The feature isn’t fully implemented yet, but you can structure the code to avoid the unimplemented sections. Manually expanding a variadic template into a parameter list won’t work. But template specialization can do that for you. template< char head, char … rest > struct … Read more

g++: error trying to exec ‘cc1plus’: execvp: No such file or directory

August 22, 2023 by Tarik

I tried the command @MonoThreaded gave but it failed. I tried below and it works. sudo apt-get install g++ Please don’t include any version after the g++.

OpenCV 2.3 Compiling Issue – Undefined Refence – Ubuntu 11.10

August 22, 2023 by Tarik

I am guessing that at least some of the libraries in the output of pkg-config opencv –libs are archive libraries. It is incorrect to put archive libraries before sources that need them (test_1.cpp in this case): the order of sources and libraries on the link line matters. Try g++ -o test_1 test_1.cpp `pkg-config opencv –cflags … Read more

Linking to MSVC DLL from MinGW

August 17, 2023 by Tarik

You can’t do this. They have exported C++ classes from their dll, rather than C-functions. The difference is, c++ functions are always exported with names in a mangled form that is specific to a particular version of the compiler. Their dll is usable by msvc only in that form, and will probably not even work … Read more

How can I force linking with a static library when a shared library of same name is present

August 16, 2023 by Tarik

You’ll need to pass the -static to the linker, but only for particular libraries you want. e.g.: g++ -o main main.cpp -Wl,-Bstatic -lmath -Wl,-Bdynamic