LPC MicrocontrollersのトピックRe: Gcc export symbols

Gcc export symbols

benoitruelland — Mon, 08 Apr 2019 19:41:19 GMT

Hi everybody,
I want to import in a project, the absolute path of a Library from another project.

For example,
I have a boot and a jump to an app. if I use printf in my boot,
I want to use the same allocation of the function printf in my app.

I Don't know with gcc/ld, how to export/import symbols

Thanks,
Benoit

Re: Gcc export symbols

Alice_Yang — Tue, 09 Apr 2019 02:41:21 GMT

Hello Benoit Ruelland,

Do you just use the GCC compiler or a IDE based on GCC?

Re: Gcc export symbols

benoitruelland — Tue, 09 Apr 2019 06:13:12 GMT

Hello,
I'm using mcuExpresso.

Re: Gcc export symbols

converse — Tue, 09 Apr 2019 08:21:48 GMT

Suggest you read this article

How to use Custom Library Names with GNU Linker and Eclipse | MCU on Eclipse

Re: Gcc export symbols

benoitruelland — Tue, 09 Apr 2019 19:13:29 GMT

Thanks Con Verse.
What I want to do is access to absolute address of function into Library in another project.

Re: Gcc export symbols

converse — Tue, 09 Apr 2019 21:05:05 GMT

Call the function in your application and link with the library containing that function. That is all you need to do.

Re: Gcc export symbols

benoitruelland — Wed, 10 Apr 2019 07:21:55 GMT

Thanks Con Verse.

a Library contain relative address for functions.
I want to access absolute address after linker process.

for illustrate, I just create a lib calculate with 2 functions
int calc_add(int a,int b)

int calc_sub(int a,int b)

In my first project I call lib_sub => linker give me this address :

.text.calc_sub
0x1a001bdc 0x1c C:\(somewhere in my computer)\Calculate\Debug\libCalculate.a(calc.o)
0x1a001bdc calc_sub

I do the same with my second project => linker give me this address :

.text.calc_sub
0x1a000f80 0x1c C:\(somewhere in my computer)\Calculate\Debug\libCalculate.a(calc.o)
0x1a000f80 calc_sub

You can see that the location of the function are not the same.

What I want to do, export symbol of my first project (Absolute address)

and import it in my second project.

For illustrate:

first project :

.text.calc_sub
0x1a001bdc 0x1c C:\(somewhere in my computer)\Calculate\Debug\libCalculate.a(calc.o)
0x1a001bdc calc_sub

second project :

.text.calc_sub
0x1a001bdc 0x1c C:\(somewhere in my computer)\Calculate\Debug\libCalculate.a(calc.o)
0x1a001bdc calc_sub

Thanks for help.

Re: Gcc export symbols

converse — Wed, 10 Apr 2019 16:50:29 GMT

Sorry, I have no idea how to do that - or even if it is possible (but it doesn't sound like a good idea).

A better way of achieving a similar outcome would be to put 'jump' table at a fixed, known location in your 1st application and then direct your call through the table in your 2nd application.