CARM: REPLACING LIBRARY FUNCTIONS

Information in this article applies to:

• CARM All Versions

QUESTION

I have defined my own putchar function. In THUMB mode everything runs fine, but when I switch to ARM mode I receive the following linker error:

*** ERROR L128: REFERENCE MADE TO UNRESOLVED EXTERNAL
    SYMBOL:  putchar?T
    ADDRESS: 0000040AH

or:

*** ERROR L104: MULTIPLE PUBLIC DEFINITIONS
    SYMBOL:  putchar?A

Is it possible to re-define a library function? Do I need to modify the run-time library?

ANSWER

You don't have to modify the compiler run-time library when you need a specially-configured version of the putchar function.

• In THUMB mode, you only need to add the library routine (since most of the CARM run-time library is also written in THUMB mode).
• In ARM mode, you need to translate the library module using the INTERWORK compiler directive. Functions translated with INTERWORK may be accessed from both CPU modes: THUMB and native ARM.

For example:

#pragma INTERWORK

#include <LPC21XX.H>          /* LPC21xx definitions */

#define CR     0x0D

int putchar (int ch)  {         /* Write to Serial Port */

  if (ch == '\n')  {
    while (!(U1LSR & 0x20));
    U1THR = CR;                 /* output CR */
  }
  while (!(U1LSR & 0x20));
  return (U1THR = ch);
}

MORE INFORMATION

• Refer to INTERWORK in the CARM User's Guide.
• Refer to Library Reference in the CARM User's Guide.

SEE ALSO

• GENERAL: PRINTF EXPANDS '0X0A' INTO '0X0A'+'0X0D'

FORUM THREADS

The following Discussion Forum threads may provide information related to this topic.

• CAL.LIB putchar function only for MCB2100 Board ???
• errormsg A108
• Scanf statement
• *** ERROR L104: MULTIPLE PUBLIC DEFINITIONS
• getchar Linker error

Last Reviewed: Tuesday, August 09, 2005