Printf() does not work or causes strange effects

1 Problem

Sometimes a simple printf() (sprintf(), snprintf(), fprintf()) function call seems to fail since no CCS ( or terminal or buffer) output occurs. In other cases a printf() conversion of integer or float seems to affect data on the stack or delays or stalls the code execution for a long time.

Please check the following steps:

2 Solution

missing include <stdio.h>.
Since printf() is a variadic function, calling such a function without a valid prototype invokes undefined behavior
missing trailing CR LF (\r\n) or flush.
By default the CCS output is line-buffered. To see the outputs close the line with CR LF or fflush(stdout);
insufficient stack size.
Make sure the stack size is at least 0x800.
insufficient heap size.
Each stream needs its own heap buffer. Make sure the heap size is at least 0x400 per stream.
Avoid C I/O inside interrupt handler functions.
C I/O functions are not reentrant and can cause a huge delay.
Stop-mode C I/O causes huge delay.
The current C I/O ABI works by setting a breakpoint at C$$IO$$. When this breakpoint is hit, the CPU is halted. The debugger then reads the contents of the .cio buffer through JTAG, performs the requested C I/O operation, writes the results back to .cio, and restarts the CPU. This is a very expensive operation in terms of cycles, and can be very disruptive in real-time systems.