Hello, (cross-posting because it is relevant to know where users need to run Kamailio as well as what developers tend to use for coding, but replies can go to one or the other list). Somehow I tried to stay close to ANSI-C/C90 with C coding style, for the reason of being compatible as much as possible with old compiles and niche/embedded systems. But I noticed that there are couple of C99 extensions in the core, like inline functions, variadic macros (the debugging macros), use of 'long long' or line comments starting with "//" (not so many, but still such comment style is used). Although I haven't searched for occurrences in core, but I remember seeing designated initializers (or initializing a structure by field names). These are part of C99, as listed by:   * https://en.wikipedia.org/wiki/C99#Design Although likely GCC had some of them like custom extensions before the standard was out. On the other hand, newer standard C11 made some of those extensions optional:   * https://en.wikipedia.org/wiki/C11_(C_standard_revision)#Optional_features So, my email here is to figure out if we should consider C99 as the requirement for adding C code or be more restrictive because there are still cases of usage on very specific systems that do not have such C compiler. We can eventually make a list of what is accepted or not from the recent versions of C standard to stay as much as possible portable across Unix'es. other projects, etc.) extensions of the new standards that they found useful and simplify their programming work. Cheers, Daniel -- Daniel-Constantin Mierla -- www.asipto.com www.twitter.com/miconda -- www.linkedin.com/in/miconda