The following subset of the GNU C language extensions is enabled with the -qlanglvl=extended option, which is the default language level.
| Language feature | Discussed in: |
|---|---|
| __alignof__ operator | The __alignof__ operator (IBM extension) |
| __imag__ and __real__ complex type operators | The __real__ and __imag__ operators (IBM extension) |
| __typeof__ operator | The typeof operator (IBM extension) |
| Assembly labels | Assembly labels (IBM extension) |
| Complex type arguments to unary operators | Unary expressions |
| Function attributes | Function attributes (IBM extension) |
| Generalized lvalues | Lvalues and rvalues |
| Placement of flexible array members anywhere in structure or union | Flexible array members |
| Statements and declarations in expressions | Statement expressions (IBM extension) |
| Static initialization of flexible array members of aggregates | Flexible array members |
| Language feature | Discussed in: | Individual option controls |
|---|---|---|
| #include_next preprocessor directive | The #include_next directive (IBM extension) | -qlanglvl=[no]gnu_include_next |
The following subset of the GNU C language extensions are enabled with the -qlanglvl=extended option, which is the default language level. These extensions can also be enabled or disabled by specific compiler options, which are listed in the below table:
| Language feature | Discussed in: | Individual option controls |
|---|---|---|
| __extension__ keyword | Keywords for language extensions (IBM extension) | -q[no]keyword=__extension__ |
| #assert, #unassert preprocessor directives | Assertion directives (IBM extension) | -qlanglvl=[no]gnu_assert |
| #include_next preprocessor directive | The #include_next directive (IBM extension) | -qlanglvl=[no]gnu_include_next |
| #warning preprocessor directive | The #warning directive (IBM extension) | -qlanglvl=[no]gnu_warning |
| Alternate keywords | Keywords for language extensions (IBM extension) | -q[no]keyword=token |
| Complex literal suffixes | Complex literals | -qlanglvl=[no]gnu_suffixij |
| Computed goto statements | Computed goto statement (IBM extension) | -qlanglvl=[no]gnu_computedgoto |
| Function attributes | Function attributes (IBM extension) | -q[no]keyword=__attribute__ |
| inline assembly-language statements | Inline assembly statements (IBM extension) | -qasm |
| Labels as values | Labels as values (IBM extension) | -qlanglvl=[no]gnu_labelvalue |
| Locally declared labels | Locally declared labels (IBM extension) | -qlanglvl=[no]gnu_locallabel |
| Type attributes | Type attributes (IBM extension) | -q[no]keyword=__attribute__ |
| typeof operator | The typeof operator (IBM extension) | -q[no]keyword=typeof |
| Variable attributes | Variable attributes (IBM extension) | -q[no]keyword=__attribute__ |
| Variadic macro extensions | Variadic macro extensions(IBM extension) | -qlanglvl=[no]gnu_varargmacros |
| Visibility function attribute | visibility (IBM extension) | -qvisibility |
| Visibility variable attribute | The visibility variable attribute (IBM extension) | -qvisibility |
| Zero-extent arrays | Zero-extent array members (IBM extension) | -qlanglvl=[no]zeroextarray |
Note: You can use the -qvisibility option
to specify visibility attributes for variables and functions if they
do not get visibility attributes from pragma directives, explicitly
specified attributes, or propagation rules. This option cannot be
used to disable visibility attributes for variables or functions.
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The following feature requires compilation with the use of an additional option, listed in the below table:
| Language feature | Discussed in: | Required compilation option |
|---|---|---|
| Dollar signs in identifiers | Characters in identifiers | -qdollar |