Trace macro failing to be called (not compiled)

Kernel
1

erupter wrote on Wednesday, June 04, 2014:

I have a basic project running, but tasks are not doing what I want so I would like to use the traceTASK_SWITCHED_IN/OUT macros to output something to a logic analyzer.

So here is my code


void setLogOutput (unsigned long c)
{
    int a;
    if (c == 0)
        a = 0;
}

#define traceTASK_SWITCHED_IN() setLogOutput(pxCurrentTCB->uxTaskNumber)
#define traceTASK_SWITCHED_OUT() setLogOutput(0)
#include "FreeRTOS.h"

Obviously setLogOutput doesn’t do anything right now, and I know it.
But the point is that neighter SWITCHED_IN nor SWITCHED_OUT are ever called or compiled.
Breakpoints in tasks.c are broken.
I cannot understand what I am doing wrong, could anybody please help me?

2

rtel wrote on Wednesday, June 04, 2014:

Where have you defined the macros?

The easiest place to put them, to get the correct include order, is at the bottom of FreeRTOSConfig.h.

Regards.

3

heinbali01 wrote on Wednesday, June 04, 2014:

Hi,

You could try:

volatile unsigned int dummy;
void setLogOutput (unsigned long c)
{
    dummy++;
}

It is possible that optimiser ignores the code, because it does nothing.

GCC is very clever with this: it sees when a variable is only used in the left-hand size of expressions, and in that case it will never be implemented. ‘volatile’ might help or better: print the variable somewhere.

Regards.

4

jdurand wrote on Wednesday, June 04, 2014:

I’ve been seeing GCC get more and more clever about working around my
ways to keep variables/code from being deleted. There was a time when
global variables were safe, but not now.

I’ve tried debugging with no optimization, but that just blows the code
up where it doesn’t fit. I now run with -Og which seems to be a
reasonable compromise most of the time.

On 06/04/2014 09:56 AM, Hein Tibosch wrote:

GCC is very clever with this: it sees when a variable is only used in
the left-hand size of expressions, and in that case it will never be
implemented. ‘volatile’ might help or better: print the variable
somewhere.

–
Jerry Durand, Durand Interstellar, Inc. www.interstellar.com
tel: +1 408 356-3886, USA toll free: 1 866 356-3886
Skype: jerrydurand

5

heinbali01 wrote on Wednesday, June 04, 2014:

Yes indeed, gcc also makes global variables disappear, even if they appear in several modules (as LHS only).

    const char ip_marker[32] = "dEfAuLtIp_192.168.2.116";
    void some_function()
    {
        __asm__ ("" : : "r" (ip_marker) : "cc");
    }

This trick worked to get a const string included in the code without ever actually reading it. Note that some_function() must be called

6

erupter wrote on Tuesday, June 10, 2014:

Sorry I thought I answered this but evidently I didn’t.

Putting the macro at the end of FreeRTOSConfig.h solved my problem.