Error handling

The library should never make the calling programs abort, nor perform any input/output operations. This decision has to be taken by the developer of the code calling the library.

All the functions return with an exit code, defined as

typedef int32_t qmckl_exit_code;

The exit code returns the completion status of the function to the calling program. When a function call completed successfully, QMCKL_SUCCESS is returned. If one of the functions of the library fails to complete the requested task, an appropriate error code is returned to the program.

Here is the complete list of exit codes.

The qmckl_string_of_error converts an exit code into a string. The string is assumed to be large enough to contain the error message (typically 128 characters).

To decode the error messages, qmckl_string_of_error converts an error code into a string.

const char*
qmckl_string_of_error (const qmckl_exit_code error);

The text strings are extracted from the previous table.

The strings are declared internally with a maximum fixed size to avoid dynamic memory allocation.

#define  QMCKL_MAX_FUN_LEN   256
#define  QMCKL_MAX_MSG_LEN  1024

typedef struct qmckl_error_struct {

  qmckl_exit_code exit_code;
  char function[QMCKL_MAX_FUN_LEN];
  char message [QMCKL_MAX_MSG_LEN];

} qmckl_error_struct;

The error is updated in the context using qmckl_set_error. When the error is set in the context, it is mandatory to specify from which function the error is triggered, and a message explaining the error. The exit code can't be QMCKL_SUCCESS.

qmckl_exit_code
qmckl_set_error(qmckl_context context,
                const qmckl_exit_code exit_code,
                const char* function_name,
                const char* message);

Upon error, the error type and message can be obtained from the context using qmckl_get_error. The message and function name is returned in the variables provided. Therefore, passing a function name and message is mandatory.

qmckl_exit_code
qmckl_get_error(qmckl_context context,
                qmckl_exit_code *exit_code,
                char* function_name,
                char* message);

To make a function fail, the qmckl_failwith function should be called, such that information about the failure is stored in the context. The desired exit code is given as an argument, as well as the name of the function and an error message. If the message is NULL, then the default message obtained by qmckl_string_of_error is used. The return code of the function is the desired return code. Upon failure, a QMCKL_NULL_CONTEXT is returned.

qmckl_exit_code
qmckl_failwith(qmckl_context context,
               const qmckl_exit_code exit_code,
               const char* function,
               const char* message) ;

For example, this function can be used as

if (x < 0) {
  return qmckl_failwith(context,
                        QMCKL_INVALID_ARG_2,
                        "qmckl_function",
                        "Expected x >= 0");
 }

Returns a string describing the last error, using qmckl_get_error.

qmckl_exit_code
qmckl_last_error(qmckl_context context, char* buffer);

The following function prints to stderr an error message is the return code is not QMCKL_SUCCESS.

qmckl_exit_code
qmckl_check(qmckl_context context, qmckl_exit_code rc);

It should be used as:

rc = qmckl_check(context,
                 qmckl_...(context, ...)
                 );
assert (rc == QMCKL_SUCCESS);