On 05/04/2011 12:32, richardcavell@xxxxxxxx wrote:
Hi, everyone. I'm building a project in C. My idea is that I want it to be mostly C89, except that I will be using certain features of C99. What compiler flags do I need to tell GCC what I want?
What are you actually trying to achieve? The only reason I can think of for someone to write C89 standard is to be compatible with more limited or older compilers. If that's the case, then you should write C89 - not C99. Many compilers that are basically C89 (or C90, or ANSI) will accept a few C99 features, such as // comments. But they are very unlikely to accept more complex C99 features, such as newer ways to handle variadic parameters. Thus your code will only work with a proper C99 compiler, and thus might as well use --std=c99.
At present, if I compile with -std=c99, I get no errors or warnings at all. If I compile with -std=c89, I get the following warnings: (When I use macros with ... and __VA_ARGS__) warning: anonymous variadic macros were introduced in C99 (When I use long string literals) warning: string length '613' is greater than the length '509' ISO C90 compilers are required to support (When I use vsnprintf) warning: implicit declaration of function 'vsnprintf' (When I initialize a struct with run-time data) warning: initializer element is not computable at load time Richard
