Robert P. J. Day wrote: > not sure if this is outside the scope of this mailing list but i > just downloaded the source for a simple SSL-aware ftp client > (netkit-ftp-ssl), did the configure and the make and got: > > ftp.c: In function ârecvrequestâ: > ftp.c:1127: error: âpdataâundeclared (first use in this function) > ftp.c:1127: error: (Each undeclared identifier is reported only once > ftp.c:1127: error: for each function it appears in.) > > ok, fair enough, check the offending header file to find the > following macro definition: > > #define is_ssl_fd(X,Y) ( (SSL_get_fd((X))==0) || \ > (SSL_get_fd((X))==1) || \ > (SSL_get_fd((X))==pdata) || \ > (SSL_get_fd((X))==(Y)) \ > > ?????. so i have a macro which accepts two arguments, but expands > to include an explicit reference to something called "pdata", which > does not exist, hence the error message. > > i tend to avoid defining macros that refer to anything but their own > arguments. what might the above mean? is there some well-known idiom > for C programmers that makes the above, in some way, acceptable? > (i've perused the code and the object "pdata", whatever that is, is > simply not defined anywhere. so is there a context in which the above > makes sense in some way?)
At the risk of stating the obvious, the only context where it makes sense is one where "pdata" is defined, as either a global variable, local variable or macro. Macros with external references are generally best avoided, although sometimes it can simplify the code signficantly. -- Glynn Clements <[EMAIL PROTECTED]> - To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
