what is --C99 in compiler option?

[Paul1]

Run the compiler as if it was the 1999 version, i.e. with features/checks/limits of back then. Useful for code that was written and tested with C99 compiler, and won't compile or run properly with current compiler.

Paul

[jhasa.1]

thank you

I have a GLCD library and use functions that was defined in it

When I use extern function define it will be error

by use --C99 comand it will be OK

[Paul1]

1. Check the compiler's manual for the syntax of the commands, maybe you have an older style than compiler default expects.
2. maybe the function was replaced/renamed in a newer version.
3. Post the section of code so others can comment on it.
4. maybe the library was compiled with an older version of the compiler, or with different options. Check library documentation, and check online about usage for the library. Search online for [error message & library name].

[TDK]

C99 is a standard and --c99 will compile code in that standard.

https://developer.arm.com/documentation/dui0491/i/Compiler-Command-line-Options/--c99?lang=en

The next standard was C11, which changed some things.

Read and interpret the error messages to debug the code.