How do I enable C++11 in gcc?

Question

I use gcc 4.8.1 from http://hpc.sourceforge.net on Mac OSX Mountain Lion. I am trying to compile a C++ program which uses the to_string function in <string>. I need to use the flag -std=c++11 every time:

g++ -std=c++11 -o testcode1 code1.cpp

Is there a way to include this flag by default?

Personally I've gone with an automator service to compile using flags like this. Makefiles are also good, and then of course there's XCode (or any other IDE). — Dave, Jun 02 '13 at 20:05
Dev-C++ and other IDEs have compiler options where you can set it — boctulus, Apr 21 '16 at 11:13

Silouane Gerin · Accepted Answer · 2013-06-02T20:11:42.733

99

H2CO3 is right, you can use a makefile with the CXXFLAGS set with -std=c++11 A makefile is a simple text file with instructions about how to compile your program. Create a new file named Makefile (with a capital M). To automatically compile your code just type the make command in a terminal. You may have to install make.

Here's a simple one :

CXX=clang++
CXXFLAGS=-g -std=c++11 -Wall -pedantic
BIN=prog

SRC=$(wildcard *.cpp)
OBJ=$(SRC:%.cpp=%.o)

all: $(OBJ)
    $(CXX) -o $(BIN) $^

%.o: %.c
    $(CXX) $@ -c $<

clean:
    rm -f *.o
    rm $(BIN)

It assumes that all the .cpp files are in the same directory as the makefile. But you can easily tweak your makefile to support a src, include and build directories.

Edit : I modified the default c++ compiler, my version of g++ isn't up-to-date. With clang++ this makefile works fine.

edited Jun 02 '13 at 20:11

answered Jun 02 '13 at 19:57

Silouane Gerin

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10
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thanks Silouane and @H2CO3 :) i should learn to work with makefiles – Guddu Jun 02 '13 at 20:16
1

@guddu : Here's a [tutorial](http://www.cs.umd.edu/class/fall2002/cmsc214/Tutorial/makefile.html) that seems a rather complete introduction. Then you might want to check [the special macros](http://www.cprogramming.com/tutorial/makefiles_continued.html) – Silouane Gerin Jun 02 '13 at 20:28
2

Worth noting that standard Makefile syntax requires tab characters, or it will give cryptic, idiotic errors. Which is why I use gmake with RECIPEPREFIX as shown in [the documentation](http://www.gnu.org/software/make/manual/make.html#Special-Variables). Tab characters are an abomination; use them never. – Parthian Shot Aug 20 '15 at 17:34
What `$^` does? And what `$<` does? – KcFnMi Oct 23 '22 at 14:37

score 27 · Answer 2 · answered Jan 12 '14 at 22:05

As previously mentioned - in case of a project, Makefile or otherwise, this is a project configuration issue, where you'll likely need to specify other flags too.

But what about one-off programs, where you would normally just write g++ file.cpp && ./a.out?

Well, I would much like to have some #pragma to turn in on at source level, or maybe a default extension - say .cxx or .C11 or whatever, trigger it by default. But as of today, there is no such feature.

But, as you probably are working in a manual environment (i.e. shell), you can just have an alias in you .bashrc (or whatever):

alias g++11="g++ -std=c++0x"

or, for newer G++ (and when you want to feel "real C++11")

alias g++11="g++ -std=c++11"

You can even alias to g++ itself, if you hate C++03 that much ;)

score 8 · Answer 3 · answered Dec 30 '15 at 17:11

8

I think you could do it using a specs file.

Under MinGW you could run
gcc -dumpspecs > specs

Where it says

*cpp:
%{posix:-D_POSIX_SOURCE} %{mthreads:-D_MT}

You change it to

*cpp:
%{posix:-D_POSIX_SOURCE} %{mthreads:-D_MT} -std=c++11

And then place it in
/mingw/lib/gcc/mingw32/<version>/specs

I'm sure you could do the same without a MinGW build. Not sure where to place the specs file though.

The folder is probably either /gcc/lib/ or /gcc/.

answered Dec 30 '15 at 17:11

DrowsySaturn

1,587
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4

1

At this point in time, it is easier to get a build of gcc-6, where the default is C++14. – Marc Glisse Dec 30 '15 at 17:22
Under Linux, you can find the location by running `strace -f gcc your-sources-here 2>&1 | grep specs`. On one (older) Debian system, this yields `/usr/lib/gcc/i586-linux-gnu/4.9/specs`. Created that `specs` as described in the answer (needs sudo to move it there under Linux) and works like a charm! Thanks. – Adrian W Oct 13 '18 at 15:12

score 0 · Answer 4 · edited Feb 07 '20 at 19:17

If you are using sublime then this code may work if you add it in build as code for building system. You can use this link for more information.

{
    "shell_cmd": "g++ \"${file}\" -std=c++1y -o \"${file_path}/${file_base_name}\"",
    "file_regex": "^(..[^:]*):([0-9]+):?([0-9]+)?:? (.*)$",
    "working_dir": "${file_path}",
    "selector": "source.c, source.c++",

    "variants":
    [
        {
            "name": "Run",
            "shell_cmd": "g++ \"${file}\" -std=c++1y -o \"${file_path}/${file_base_name}\" && \"${file_path}/${file_base_name}\""
        }
    ]
}

How do I enable C++11 in gcc?

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