--apcs=qualifer...qualifier

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2.1.4.Â `--apcs=qualifer...qualifier`

This option controls interworking and position independence when generating code.

By specifying qualifiers to the â€'â€'apcs commandâ€'line option, you can define the variant of the Procedure Call Standard for the ARM architecture (AAPCS) used by the compiler.

Syntax

--apcs=qualifer...qualifier

Where qualifier...qualifier denotes a list of qualifiers. There must be:

at least one qualifier present
no spaces separating individual qualifiers in the list.

Each instance of qualifier must be one of:

/[no]interwork

Generates code with or without ARM/Thumbâ„¢ interworking support. The default is /nointerwork.

/[no]ropi

Enables or disables the generation of Readâ€'Only Positionâ€'Independent (ROPI) code. The default is /noropi.

/[no]pic is an alias for /[no]ropi.

/[no]rwpi

Enables or disables the generation of Read/Write Positionâ€'Independent (RWPI) code. The default is /norwpi.

/[no]pid is an alias for /[no]rwpi.

Note

You can alternatively specify multiple qualifiers. For example, --apcs=/nointerwork/noropi/norwpi is equivalent to --apcs=/nointerwork --apcs=noropi/norwpi.

Default

If you do not specify an â€'â€'apcs option, the compiler assumes â€'â€'apcs=/nointerwork/noropi/norwpi.

Usage

/[no]interwork

By default, code is generated:

without interworking support, that is /nointerwork, unless the device you select using the â€'â€'device=name option corresponds to architecture ARMv5T or later
with interworking support, that is /interwork, for ARMv5T or later. This is because ARMv5T or later provides direct interworking support.

/[no]ropi

If you select the /ropi qualifier to generate ROPI code, the compiler:

addresses readâ€'only code and data PCâ€'relative
sets the Position Independent (PI) attribute on readâ€'only output sections.

Note

â€'â€'apcs=/ropi is not supported when compiling C++.

/[no]rwpi

If you select the /rwpi qualifier to generate RWPI code, the compiler:

addresses writable data using offsets from the static base register sb. This means that:
- the base address of the RW data region can be fixed at runtime
- data can have multiple instances
- data can be, but does not have to be, positionâ€'independent.
sets the PI attribute on read/write output sections.

Note

Because the â€'â€'lower_rwpi option is the default, code that is not RWPI is automatically transformed into equivalent code that is RWPI. This static initialization is done at runtime by the C++ constructor mechanism, even for C.

Restrictions

There are restrictions when you compile code with /ropi or /rwpi.

/ropi

The main restrictions when compiling with /ropi are:

The use of â€'â€'apcs=/ropi is not supported when compiling C++.
Some constructs that are legal C do not work when compiled for â€'â€'apcs=/ropi. For example:
```
extern const int ci; // ro
const int *p2 = &ci; // this static initialization
                     // does not work with â€'â€'apcs=/ropi
```
To enable such static initializations to work, compile your code using the â€'â€'lower_ropi option. For example:
```
armcc â€'â€'apcs=/ropi â€'â€'lower_ropi
```

/rwpi

The main restrictions when compiling with /rwpi are:

Some constructs that are legal C do not work when compiled for â€'â€'apcs=/rwpi. For example:

int i; Â Â Â Â Â Â Â Â Â Â Â Â Â Â // rw
int *p1 = &i; Â Â Â Â Â Â Â // this static initialization
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â // does not work with â€'â€'apcs=/rwpi
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â // â€'â€'no_lower_rwpi

To enable such static initializations to work, compile your code using the â€'â€'lower_rwpi option. For example:

armcc â€'â€'apcs=/rwpi

Note

You do not have to specify â€'â€'lower_rwpi, because this is the default.

2.1.4.Â --apcs=qualifer...qualifier

Syntax

Note

Default

Usage

Note

Note

Restrictions

Note

See also

2.1.4.Â `--apcs=qualifer...qualifier`