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Insert assembly code into a C program

Good day,

I would like to use an existing function with assembly code in a C program.

Unfortunately I don't know the exact syntax for this.

Of course, I also searched for it on the Internet (I probably didn't use the right search terms):

I found: “You have to read the documentation”.

I did that too and found:

1. at: https://developer.arm.com/documentation/101655/0961/Cx51-User-s-Guide/Compiling-Programs/Directives/Reference/ENDASM-Compiler-Directive?lang=en

The example:

extern void test();

void main (void) {

test(); #pragma asm

JMP$; endless loop

#pragma endasm 
} 

but it's not understandable to me.

If I in my C program

#pragma asm 
    JMP$; endless loop 
#pragma endasm 

insert,

I get the following error message:

lcd_at89C51_2.c(113): error C272: 'asm/endasm' requires src-control to be active

lcd_at89C51_2.c(115): error C272: 'asm/endasm' requires src-control to be active

Of course I have completed this point (it is the default)

None.

µVision

1. Right click on the file in the Project Window — Files tab

2. Choose Options for... to open Options — Properties page

3. Enable Generate Assembler SRC file

4. Enable Assemble SRC file.

I understand the example shown to be the assembler code of an external file (extern void test ();) ?

If so, what should this file look like and with what ending (file.?)

2. at: https://developer.arm.com/documentation/dui0375/g/Compiler-specific-Features/--asm

This post doesn't help me either.

It seems to be possible that you can insert assembly code into a C program and compile it, but it would be nice for me if I could do this in a working example.

Kind Regards

Juergen B.

Parents
  • One thing isn't quite clear from your description of what you're trying to do: do you want assembly code in a C program, or inside a C source file?

    The former is a whole lot easier than the latter, because it can usually be achieved even without explicit compiler support: just write a dummy implementation of that function in C, compile it to assembler source, copy that and then fill in the ultra-special things you think you can only do in assembler.

    The latter is usually referred to as "in-line assembly", and is entirely compiler-specific.  You really will have to read essentially all the applicable documentation to do it without risking the stability of the surrounding C code.

Reply
  • One thing isn't quite clear from your description of what you're trying to do: do you want assembly code in a C program, or inside a C source file?

    The former is a whole lot easier than the latter, because it can usually be achieved even without explicit compiler support: just write a dummy implementation of that function in C, compile it to assembler source, copy that and then fill in the ultra-special things you think you can only do in assembler.

    The latter is usually referred to as "in-line assembly", and is entirely compiler-specific.  You really will have to read essentially all the applicable documentation to do it without risking the stability of the surrounding C code.

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