implicit declaration of function 'ITM_SenderChar' is invalid in C99 issue in KEIL

1.8k Views Asked by ele_911 At 03 April 2025 at 18:30

I came across the warning message as follow from Keil's uVision at the cortex-m3's "HELLO" example.

warning: implicit declaration of function 'ITM_SenderChar' is invalid in C99

when I implement ITM_SendChar('\r');

what am I supposed to do to resolve this problem?

below is snippet code

int fputc(int c, FILE *f) {
  if (c == '\n')  {
    ITM_SendChar('\r'); //<== invalid?
  }
  return(ITM_SendChar(c)); 
}

update

you can see the warning message from above image. and one more thing, If I click 'Goto the definition ITM_SenderChar' on pop-up menu, then

the browse window is appearing.

There are 1 best solutions below

ele_911 On 29 August 2017 at 08:42

As old_timer said, I resolve this issue by adding Core_cm3.h in "CMSDK_CM3.h". this issue happens due to lack of declaration.