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April 19, 2014 Defining symbols in a linker script | ||||
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Hello, It is common practice in ARM Cortex-M bare metal C/C++ programs to define symbols in the linker so one can initialize the .data and .bss segments and know the boundaries of one's stack and heap. It looks something like this. **** linkerscript **** __text_end__ = .; .data : AT(__text_end__) { __data_start__ = .; *(.data) *(.data.*) __data_end__ = .; } > SRAM **** C++ file **** extern "C" uint32_t __text_end__; extern "C" uint32_t __data_start__; extern "C" uint32_t __data_end__; void startup() { // copy mutable state out of ROM into RAM memcpy(&__data_start__, &__text_end__, (&__data_end__ - &__data_start__) * 4); } I tried to do something similar in D with... extern(C) __gshared uint __text_end__; extern(C) __gshared uint __data_start__; extern(C) __gshared uint __data_end__; ... but unfortunately this puts new variables in the .bss segment. I want the un-mangled name, so I can refer to it easily, but I also want it to be truly "extern" (defined elsewhere). Is that possible at this moment in D? Thanks for the help, Mike |
April 19, 2014 Re: Defining symbols in a linker script | ||||
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Posted in reply to Mike Attachments:
| On 19 Apr 2014 01:35, "Mike via D.gnu" <d.gnu@puremagic.com> wrote: > > Hello, > > It is common practice in ARM Cortex-M bare metal C/C++ programs to define symbols in the linker so one can initialize the .data and .bss segments and know the boundaries of one's stack and heap. It looks something like this. > > **** linkerscript **** > __text_end__ = .; > > .data : AT(__text_end__) > { > __data_start__ = .; > *(.data) > *(.data.*) > __data_end__ = .; > } > SRAM > > **** C++ file **** > extern "C" uint32_t __text_end__; > extern "C" uint32_t __data_start__; > extern "C" uint32_t __data_end__; > > void startup() > { > // copy mutable state out of ROM into RAM > memcpy(&__data_start__, &__text_end__, (&__data_end__ - &__data_start__) * 4); > } > > I tried to do something similar in D with... > > extern(C) __gshared uint __text_end__; > extern(C) __gshared uint __data_start__; > extern(C) __gshared uint __data_end__; > > ... but unfortunately this puts new variables in the .bss segment. I want the un-mangled name, so I can refer to it easily, but I also want it to be truly "extern" (defined elsewhere). Is that possible at this moment in D? > > Thanks for the help, > Mike I think you mean to 'extern (C) extern' Iain |
April 19, 2014 Re: Defining symbols in a linker script | ||||
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Posted in reply to Iain Buclaw | On Saturday, 19 April 2014 at 01:50:45 UTC, Iain Buclaw via D.gnu wrote:
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> I think you mean to 'extern (C) extern'
>
Yes, that's what I was looking for. Thanks.
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