It's a macro I define in log.h. It uses something I think is specific
to gcc, called "stringification", which is invoked by using a macro
parameter with a '#' in front of it. Here's the macro definition:
// macro to log fields in structs.
#define log_struct(st, field, format, typecast) \
log_msg(" " #field " = " #format "\n", typecast st->field)
For instance, when I use the macro from log_fi() (in log.c) with
log_struct(fi, flags, 0x%08x, );
The macro expands to
