Switching between ABI modes

Symbian OS natively runs on ARM processors and to build a Symbian OS application, we need a compiler based on the Application Binary Interface (ABI) for ARM Architecture. There are two versions of the ARM ABI, referred to as v1 and v2 respectively. The Symbian OS build toolchain defines a set of native build targets (ARMV5 and ARMV6) that invoke ARM's RealView Compiler Tools (RVCT) to build binaries conforming to these two ABI versions. For more information on differences between ABI v1 and v2 toolchains, refer to ABIv1 to ABIv2 toolchain changes.

From Symbian OS v9.4 onwards, the behaviour of these build targets (ARMV5, ARMV5_ABIv2, ARMV6 and ARMV6_ABIv2) can be changed. The following lists the behaviour of these build targets prior to, for and after Symbian OS v9.4:

• For Symbian OS v9.3 and earlier versions, the build targets used to create binaries conforming to ABI v1 and ABI v2 are ARMV5 and ARMV5_ABIv2 respectively, and ARMV6 and ARMV6_ABIv2 respectively. By default, the abld build command will create binaries conforming to ARMV5 ABI v1.

• For Symbian OS v9.4 and later, the build targets used to create binaries conforming to ABI v2 and ABI v1 are ARMV5 and ARMV5_ABIv1 respectively, and ARMV6 and ARMV6_ABIv1 respectively. By default, the abld build command will create binaries conforming to ARMV5 ABI v2.

You can choose to switch between the above listed behaviours using the macro ENABLE_ABIV2_MODE. If you enable this macro, the behaviour of build targets ARMV5 and ARMV6 is changed to create binaries conforming to ABI v2 instead of ABI v1. If you want to create binaries conforming to ABI v1, use the build targets ARMV5_ABIv1 and ARMV6_ABIv1.

To switch to ABI v2 mode from ABI v1 mode, edit the variant.cfg file located at epoc32\tools\variant\ and add the macro ENABLE_ABIV2_MODE.

After you add the macro to variant.cfg file, the following abld commands will create binaries conforming to ABI v2 under epoc32\release\ARMV5\ or epoc32\release\ARMV6\ folders:

> abld build

> abld build ARMV5

> abld build ARMV6

If you want to create binaries conforming to ABI v1 under epoc32\release\ARMV5_ABIV1\ or epoc32\release\ARMV6_ABIV1\ folders, use the following abld commands:

> abld build ARMV5_ABIV1

> abld build ARMV6_ABIV1

A summary of the available build targets, their instruction set, compiler version, ABI version and their target location, after you switch to ABI v2 mode is as follows:

Target name	Instruction set	Compiler	ABI	Target location
ARMV5	v5	RVCT 2.2 Build 616	v2	epoc32\release\ARMV5\
ARMV5_ABIv1	v5	RVCT 2.2 Build 616	v1	epoc32\release\ARMV5_ABIV1\
ARMV6	v6	RVCT 2.2 Build 616	v2	epoc32\release\ARMV6\
ARMV6_ABIv1	v6	RVCT 2.2 Build 616	v1	epoc32\release\ARMV6_ABIV1\
GCCE	v5	GCCE	v2	epoc32\release\gcce\

To switch back to ABI v1 mode from ABI v2 mode, disable the ENABLE_ABIV2_MODE macro. You can disable the macro either by commenting it or removing it from the variant.cfg file.

After you disable the ENABLE_ABIV2_MODE macro, the following abld commands will create binaries conforming to ABI v1 under epoc32\release\ARMV5\ or epoc32\release\ARMV6\ folders:

> abld build

> abld build ARMV5

> abld build ARMV6

If you want to build binaries conforming to ABI v2 under epoc32\release\ARMV5_ABIV2\ or epoc32\release\ARMV6_ABIV2\ folders, use the following abld commands:

> abld build ARMV5_ABIV2

> abld build ARMV6_ABIV2