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Instruct XDC to treat enums as integer [message #511668]

Tue, 02 February 2010 08:44

Eclipse User

Hi,

I am faced with a problem on packed enums, by default the enums are converted to short integers. This could potentially break my software. I want to instruct XDC to treat enums as integers.

As per XDC documentation, its possible to do so by specifying "M3.model.shortEnums = false;" where M3 is a variable of type ti.targets.arm.elf.M3 in config.bld

When built with this modification, I get following error.

"E:/Work/packages/config.bld", line 26: XDC
runtime error: ti.targets.arm.elf.M3/model: 'shortEnums' is sealed
.interfaces files complete: Tue Feb 2 19:10:24 IST 2010.

Could you please help me out with this? I am using RTSC/XDC versioned 3.16.01.27

Thanks,
Sujith

Re: Instruct XDC to treat enums as integer [message #511778 is a reply to message #511668]

Tue, 02 February 2010 14:18

Eclipse User

Sujith,

The basic problem with your approach is that you are trying to change the definition of an existing Target.
http://rtsc.eclipse.org/docs-tip/Glossary#Target
The shortEnums property is configured when a Target is defined and cannot be changed subsequently. Why? If you changed it, you would no longer be compiling code in a compatible fashion with the original Target. You could define a new Target that specifies shortEnums = false and then use that Target when building your code. However, you would then need to re-compile any other packages you use with this new target so they would be compatible. Probably now what you want.

There may be another way to do what you want on a per structure or enum basis without changing the Target.

Or, do you think that the way ti.targets.arm.elf.M3 is wrong and it should be using shortEnums = false?

Mark

Re: Instruct XDC to treat enums as integer [message #511884 is a reply to message #511778]

Wed, 03 February 2010 05:39

Eclipse User

Mark,

Thanks for the response. I could create a new target and define shortEnums = false. I will have to explore methods to define a new target.

But,
M3 could be part of multi-core system hosting multiple/different OSes. (With different compiler characteristic of treating an enum could be packed/un-packed) If were to have IPC between these core (say shared memory communication), we would run into issues on the structure sizes.

I think it would be a good idea to set it false by default, for optimizations user could define a custom target and define the enum behavior among other characteristic.

Thanks,
Sujith

Re: Instruct XDC to treat enums as integer [message #512397 is a reply to message #511668]

Thu, 04 February 2010 17:12

Eclipse User

The whole 'shortEnums' functionality is added because of https://bugs.eclipse.org/bugs/show_bug.cgi?id=289018.

By default, TI's Arm compiler packs enums. That can be verified by looking into the section $build.attributes, and decoding it as specified in the section 2.3.6.2 The procedure call-related attributes, in http://infocenter.arm.com/help/topic/com.arm.doc.ihi0045c/IH I0045C_ABI_addenda.pdf.

The TI Arm compiler has the option --enum_type=unpacked,int,packed, designate enum type (Default is packed for EABI). If we were passing that option for our M3 target, shortEnum would be false. I don't know if there is a good reason that we should, but the linker would certainly complain if the object files with different enum options were linked together. That means that the different shortEnum options require two different M3 targets.

[Updated on: Thu, 04 February 2010 17:53] by Moderator

Re: Instruct XDC to treat enums as integer [message #512444 is a reply to message #512397]

Fri, 05 February 2010 02:54

Eclipse User

Thanks, I get the rational behind default enum configuration. To solve the issue that I am facing, I will define a new target and turn off this flag.

Thanks,
Sujith

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