ColdFire/68K Microcontrollers and Processors中的主题 Re: referensing global labels fails

referensing global labels fails

Veter — Thu, 22 Mar 2007 21:47:56 GMT

I am trying to reference global label located in the startup.s source from *.cpp file.

The error message states that label is "Undefined".

Assembly code:

.section .init$00,2,C

.global ___init
___init

; Linker places .init sections from other modules, containing
; calls to initialize global objects, here.

.section .init$99,2,C

rts ; Return from ___init.

C++ code:

extern void ___init(void);

static int init_main_guts(void)
{

...

/* initialize constructors */
___init();

...

}

What am I doing wrong?

I am using CodeWarrior Development Studio for ColdFire Architectures Version 6.3, Build 14.

My target is MCF5307.

Thank you!

Re: referensing global labels fails

SimonMarsden_de — Thu, 22 Mar 2007 23:56:38 GMT

The CodeWarrior C compiler adds an underscore to the start of every function name, but in assembler you need to add it yourself.

Thus a function in the C source code called foo() needs to be referred to as "_foo" in the assembler source.

It looks like you've got one too many '_' characters in the ___init() call in main.c

Cheers

Simon

Re: referensing global labels fails

Veter — Thu, 22 Mar 2007 23:58:54 GMT

That is correct. There is one extra "_" character. Olso "__init()" does not need parenthesis. The working code has "__init;".

Thank you.

Re: referensing global labels fails

CompilerGuru — Fri, 23 Mar 2007 05:28:16 GMT

Veter wrote:
Olso "__init()" does not need parenthesis. The working code has "__init;".
Thank you.

__init;

is an statement without any side effect in C. Legal, but useless.
So if you do want __init to be called, add the parenthesis again.
Daniel

Re: referensing global labels fails

Veter — Sat, 24 Mar 2007 03:09:36 GMT

Daniel,

If I add parenthesis I get following error:

Link Error : Undefined : "__init()"

I do not have such error without them.

Any ideas?

Re: referensing global labels fails

CompilerGuru — Sat, 24 Mar 2007 07:34:51 GMT

I just noted one little word in the initial post:

C++ code:

Does this mean init_main_gut is contained in a C++ file?
Well, that would explain it. In order to use C (or assembly for that matter) stuff from C++, it has to be explicitly given the C linkage.

#ifdef __cplusplus
extern "C" {
#endif
extern void __init(void);
#ifdef __cplusplus
}
#endif

static int init_main_guts(void)
{
...
 /* initialize constructors    */
 __init();
...
}

Also something to check: can you disassemble both the assembly and the C++ (or C) file,
and compare how the two __init names look like. They have to be identical.
To disassemble, use the context menu in the project window. There is also a preference panel to configure the disassembler.

Daniel

Re: referensing global labels fails

Veter — Mon, 26 Mar 2007 20:21:15 GMT

That was it.

Including 'extern "C" {}' directive solved the problem.

Dissasemblies for both sources look the same now.

Thank you!