Error Reporting & Debugging

The debug-print macros W_DEBUG and W_DEBUGC produce messages on standard error when _DEBUG_PRINT is defined before including the wheel.h header., By default their expansion are empty statements. The following builds program.c with the debug-print statements turned on:

cc -D_DEBUG_PRINT -o program program.c

The W_FATAL and W_BUG macros can be used to produce fatal errors which abort execution of the program.

The W_WARN macro can be used to produce non-fatal warnings, which can optionally be converted into fatal warnings at run-time when programs are run with the W_FATAL_WARNIGS environment variable defined to a non-zero value in their environment.

The w_die() function can be used to exit a program gracefully after printing an error message to standard error.

Macros

W_DEBUG(const char *format, ...)

Produces a debug-print on standard error with the given format. The macro automatically adds the function name, file name and line number to the message.

If _DEBUG_PRINT is not defined (the default), this macro expands to an empty statement, causing no overhead.

See Formatted output for the available formatting options.

W_DEBUGC(const char *format, ...)

Produces a “continuation” debug-print on standard error with the given format. The macro does not add the function name, file name and line number to the message (hence “continuation”).

If _DEBUG_PRINT is not defined (the default), this macro expands to an empty statement, causing no overhead.

See Formatted output for the available formatting options.

W_FATAL(const char *format, ...)

Writes a fatal error message to standard error with the given format, and aborts execution of the program. The macro automatically adds the function name, file name and line number where the fatal error is produced.

See Formatted output for the available formatting options.

W_BUG(const char *message)

Marks the line where the macro is expanded as a bug: if control ever reaches the location, a fatal error is produced using W_FATAL instructing the user to report the issue. The date and time of the build are included in the error message.

It is possible to supply an optional message to be printed next to the supplied text. Note that, if supplied, this should be a hint to help developers of the program.

Note that, as the message is optional, both these macro expansions produce valid code:

W_BUG();
W_BUG("This is a bug");

W_WARN(format, ...)

Writes a warning to standard error with the given format. The macro automatically adds the function name, file name and line number where the warning is produced.

See Formatted output for the available formatting options.

If the W_FATAL_WARNINGS environment variable is defined and its value is non-zero, warnings are converted into W_FATAL errors and execution of the program will be aboerted.

Functions

void w_die(const char *format, ...)

Prints a message to standard error with a given format and exits the program with the EXIT_FAILURE status code.

See Formatted output for the available formatting options.