How to enable debug prints

Duktape 1.x

• Enable DUK_OPT_DEBUG / DUK_USE_DEBUG
• Enable DUK_OPT_DPRINT / DUK_USE_DPRINT for minimal logs
• Enable also DUK_OPT_DDPRINT / DUK_USE_DDPRINT for verbose logs
• Enable also DUK_OPT_DDDPRINT / DUK_USE_DDDPRINT for very verbose logs

Logs will be written to stderr.

Duktape 2.x

• Enable DUK_USE_DEBUG
• Define DUK_USE_DEBUG_LEVEL=<n> where n is 0 for minimal logs, 1 for verbose logs, and 2 for very verbose logs
• Define DUK_USE_DEBUG_WRITE(level,file,line,func,msg) to write out log entries; this allows you to fully control where debug logs should go

Example of DUK_USE_DEBUG_WRITE in manually edited duk_config.h:

#define DUK_USE_DEBUG_WRITE(level,file,line,func,msg) do { \
        fprintf(stderr, "D%ld %s:%d (%s): %s\n", \
                (long) (level), (file), (long) (line), (func), (msg));
    } while (0)

Same function as an argument to tools/configure.py:

'-DDUK_USE_DEBUG_WRITE(level,file,line,func,msg)=do {fprintf(stderr, "D%ld %s:%ld (%s): %s\n", (long) (level), (file), (long) (line), (func), (msg));} while(0)'