The Compiler Seems to Generate Incorrect Code.

First, determine if the code is incorrect or not. Sometimes the operator-precedence rules of ANSI-C do not quite give the results one would expect. Sometimes faulty code can appear to be correct. Consider the example in the following listing:

Listing: Possibly faulty code?

if (x & y != 0) ...
evaluates as:
if (x & (y != 0)) ...
but not as:
if ((x & y) != 0) ...

Another source of unexpected behavior can be found among the integral promotion rules of C. Characters are usually (sign-)extended to integers. This can sometimes have quite unexpected effects, e.g., the if condition in the following listing is FALSE:

Listing: if condition is always FALSE

 unsigned char a, b;
  b = -8;

  a = ~b;

  if (a == ~b) ...

because extending a results in 0x0007, while extending b gives 0x00F8 and the ' ~' results in 0xFF07. If the code contains a bug, isolate the construct causing it and send a bug report to Freescale support.