Is there a compiler compatibility flag for C++ like -std=c99 ? Or is there some other way to get new g++ compilers to not choke on old code?

Yes, C++ compiler uses the same flag like the C compiler, so just use the -std= option with one of the following values:

• c++98: The 1998 ISO C++ standard plus amendments. Same as -ansi for C++ code.
• gnu++98: GNU dialect of -std=c++98. This is the default for C++ code.
• c++0x: The working draft of the upcoming ISO C++0x standard. This option enables experimental features that are likely to be included in C++0x. The working draft is constantly changing, and any feature that is enabled by this flag may be removed from future versions of GCC if it is not part of the C++0x standard.
• gnu++0x: GNU dialect of -std=c++0x. This option enables experimental features that may be removed in future versions of GCC.

- Andi -

Ah, thanks very much. I'm pretty sure I did try std=c++99 and got an error about unrecognized option, so I'll probably have to rebuild the compiler to enable the support for it.

What version of gcc/g++ are you using? (gcc -v)

- Andi -

Well, various. My main compiler right now is 4.4.2, but I have 4.3.2 and 4.2.1. When I have something really old to compile, I usually break down and use 3.4.6 which I have st up as an alternative compiler. 4.3.2 and 4.2.1 are both candidates for my main compiler -I have my own home-grown system so I can settle on any one of them in the end, thoguh 4.4.2 would be the best bet since I am using glibc-2.11.1. I pretty sure that gcc-4.3.2 supports the --enable-c99 configuration option, but do I need to pass --enable-c++99 as well?

Is using the -ansi compiler option comparable, or is that only for C?

Okay, 4.4.2 looks quite recent ;-)

I don't know about these options - which doesn't mean they don't exist - but I can't find any indications in 4.4.2 at least that the -std options depend on the configure input. As far as I know, the -std=* options should be valid for the default configuration of gcc/g++.

Here's the comment from the man page:

-ansi: In C mode, this is equivalent to -std=c89. In C++ mode, it is equivalent to -std=c++98.

- Andi -