1.4 ISO C99

The compiler compiles ISO C99 C and also supports ARM extensions to ISO C99.

The compiler compiles C as defined by the 1999 C standard and addenda:

  • ISO/IEC 9899:1999. The 1999 International Standard for C.

  • ISO/IEC 9899:1999/Cor 2:2004. Technical Corrigendum 2.

The compiler also supports several extensions to ISO C99.

Throughout this document, the term:


Means ISO C99, together with the ARM and GNU extensions.

Use the compiler option --c99 to compile C99 code.

Strict C99

Means C as defined by the 1999 C standard and addenda.

Use the compiler options --c99 --strict to compile strict C99 code.

Standard C

Means C90 or C99 as appropriate.


Means any of C90, strict C90, C99, strict C99, and Standard C.

Related reference
8.24 --c99
8.173 --strict, --no_strict
1.6 Language extensions
1.7 Language compliance
15.1 Implementation definition
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