Compiling with GCCsuggest change
Assuming a single source file named
main.cpp, the command to compile and link an non-optimized executable is as follows (Compiling without optimization is useful for initial development and debugging, although
-Og is officially recommended for newer GCC versions).
g++ -o app -Wall main.cpp -O0
g++ -o app -Wall -O2 main.cpp
If the -O option is omitted, -O0, which means no optimizations, is used as default (specifying -O without a number resolves to -O1).
Alternatively, use optimization flags from the
O groups (or more experimental optimizations) directly. The following example builds with
-O2 optimization, plus one flag from the
-O3 optimization level:
g++ -o app -Wall -O2 -ftree-partial-pre main.cpp
To produce a platform-specific optimized executable (for use in production on the machine with the same architecture), use:
g++ -o app -Wall -O2 -march=native main.cpp
Either of the above will produce a binary file that can be run with
.\app.exe on Windows and
./app on Linux, Mac OS, etc.
g++ -o file.o -Wall -c file.cpp
This produces an object file named
file.o which can later be linked with other files to produce a binary:
g++ -o app file.o otherfile.o
More about optimization options can be found at gcc.gnu.org. Of particular note are
-Og (optimization with an emphasis on debugging experience – recommended for the standard edit-compile-debug cycle) and
-Ofast (all optimizations, including ones disregarding strict standards compliance).
-Wall flag enables warnings for many common errors and should always be used. To improve code quality it is often encouraged also to use
-Wextra and other warning flags which are not automatically enabled by
If the code expects a specific C++ standard, specify which standard to use by including the
-std= flag. Supported values correspond to the year of finalization for each version of the ISO C++ standard. As of GCC 6.1.0, valid values for the
std= flag are
c++1z. Values separated by a forward slash are equivalent.
g++ -std=c++11 <file>
GCC includes some compiler-specific extensions that are disabled when they conflict with a standard specified by the
-std= flag. To compile with all extensions enabled, the value
gnu++XX may be used, where
XX is any of the years used by the
c++ values listed above.
The default standard will be used if none is specified. For versions of GCC prior to 6.1.0, the default is
-std=gnu++03; in GCC 6.1.0 and greater, the default is
Note that due to bugs in GCC, the
-pthread flag must be present at compilation and linking for GCC to support the C++ standard threading functionality introduced with C++11, such as
std::wait_for. Omitting it when using threading functions may result in no warnings but invalid results on some platforms.
Linking with libraries:
-l option to pass the library name:
g++ main.cpp -lpcre2-8 #pcre2-8 is the PCRE2 library for 8bit code units (UTF-8)
If the library is not in the standard library path, add the path with
g++ main.cpp -L/my/custom/path/ -lmylib
Multiple libraries can be linked together:
g++ main.cpp -lmylib1 -lmylib2 -lmylib3
If one library depends on another, put the dependent library before the independent library:
g++ main.cpp -lchild-lib -lbase-lib
Or let the linker determine the ordering itself via
--end-group (note: this has significant performance cost):
g++ main.cpp -Wl,--start-group -lbase-lib -lchild-lib -Wl,--end-group