CohereSim: A Bus-based Cache Simulator  v3.3
A tool for education in computing - learn about coherence protocols, replacement policies, and SMP vs DSM
Exit Codes

Table of Contents

The exit code provides an indicator as to which exact argument has caused an error. This value may seem redundant as this information is also printed to stderr, but it's purpose is to make programmatic interaction with CohereSim (scripting) easier.

Specific Values

  • -1 (255 in Linux): The number of arguments passed does not match any valid argument list
  • 0: The program has executed normally
  • 1-8: The nth argument on the command line is invalid
  • Any other value falls under the general format category

General Format

The general format is used when running the program in batch metrics mode, that is, a file containing multiple cache configurations was specified. It is comprised of two bit fields:

  • The lower 3 bits deterimine the index of the offending argument
  • The remaining bits determine which configuration has caused the error (5 bits on Linux)

The numbering of the arguments, which gets stored in the lower 3 bits, is 1-6 as defined in main.cc, specifically args_single_e.

Limitations

It is worth noting that in Linux, the exit code of a program or shell script is only 8 bits. For instance, if a program returns -1, then the value stored in the $? variable will be 255. This means that a maximum of 31 (5 bit count starting at 1) configurations are supported without the potential for overflow in the exit code. For this reason, the exit code is also printed to stderr in the format arg@conf, where arg indicates which argument and conf which configuration (0 for command line) caused the error.

On Windows, this issue does not exist as the full 32 bits of the exit code are available to the shell.

Examples

After issuing echo $?, the output was:

  • 3 -> Specific value: The 3rd argument on the command line caused an issue
  • 42 -> General format 00101_010: The line size (2nd) argument of the 5th configuration in the configuration file caused an issue
  • 62 -> General format 00111_110: The directory (6th) argument of the 7th configuration in the configuration file caused an issue
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