Welcome to Software Development on Codidact!
Will you help us build our independent community of developers helping developers? We're small and trying to grow. We welcome questions about all aspects of software development, from design to code to QA and more. Got questions? Got answers? Got code you'd like someone to review? Please join us.
Post History
To use this StackExchange answer as a starting point, the latest POSIX standard does not specify a cc command at all: POSIX 1003.1-2001 (Single Unix v3) specifies c99 instead of c89, to use an u...
Answer
#1: Initial revision
To use [this StackExchange answer](https://unix.stackexchange.com/a/379452) as a starting point, the latest POSIX standard does not specify a `cc` command at all: > POSIX 1003.1-2001 (Single Unix v3) specifies `c99` instead of `c89`, to use an updated standard dialect of C. You can see some editorial traces left from a draft that included a cc utility as well, but cc was removed from the specification. POSIX 1003.1-2008 (Single Unix v4) again just has `c99` So you can't rely on the _existence_ of a `cc` command, much less its options. If we look at what the [latest POSIX actually says](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/c99.html) about the `c99` command, there is no reference to an `-isystem` option. So I think the answer to your question is no. If you want to rely strictly on POSIX-mandated compiler options, you cannot use `-isystem`.