[fpc-pascal] Translating from error numbers to symbolic name
When using a function like fpAccept on a non-blocking socket, in some cases -1 is returned with a documented (Linux kernel) error code of EAGAIN. Should I be looking for this in errno or SocketError? When I've retrieved a numeric code from errno or SocketError, is there a way of converting it to a concise literal such as 'EAGAIN'? I want the log to report that accept() has failed with EAGAIN, rather than having explanatory text that doesn't match the kernel documentation. -- Mark Morgan Lloyd markMLl .AT. telemetry.co .DOT. uk [Opinions above are the author's, not those of his employers or colleagues] ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Translating from error numbers to symbolic name
In our previous episode, Mark Morgan Lloyd said: > When using a function like fpAccept on a non-blocking socket, in some > cases -1 is returned with a documented (Linux kernel) error code of > EAGAIN. Should I be looking for this in errno or SocketError? Socketerror is more portable, but on *nix errno will work too. > When I've retrieved a numeric code from errno or SocketError, is there a > way of converting it to a concise literal such as 'EAGAIN'? See errors unit. > I want the > log to report that accept() has failed with EAGAIN, rather than having > explanatory text that doesn't match the kernel documentation. EAGAIN generally means that you should try again. So repeat until repeat res:=dofunc; err:=geterrno; until (res<>-1) or ((err<>ESysEINTR) and (err<>ESysEAgain)); it is a workaround against potential deadlock between userland and kernel iirc. Retrying means it can simple work. ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Translating from error numbers to symbolic name
Marco van de Voort wrote: In our previous episode, Mark Morgan Lloyd said: When using a function like fpAccept on a non-blocking socket, in some cases -1 is returned with a documented (Linux kernel) error code of EAGAIN. Should I be looking for this in errno or SocketError? Socketerror is more portable, but on *nix errno will work too. Thanks, found that in the source. When I've retrieved a numeric code from errno or SocketError, is there a way of converting it to a concise literal such as 'EAGAIN'? See errors unit. But if I'm reading that properly, it translates (some OS-specific number) to 'Try again', not to 'EAGAIN' which is what the kernel docs refer to and which can reasonably be logged without requiring i18n. I want the log to report that accept() has failed with EAGAIN, rather than having explanatory text that doesn't match the kernel documentation. -- Mark Morgan Lloyd markMLl .AT. telemetry.co .DOT. uk [Opinions above are the author's, not those of his employers or colleagues] ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
Re: [fpc-pascal] Translating from error numbers to symbolic name
On 8/3/2012 18:24, Marco van de Voort wrote: EAGAIN generally means that you should try again. So repeat until repeat res:=dofunc; err:=geterrno; until (res<>-1) or ((err<>ESysEINTR) and (err<>ESysEAgain)); it is a workaround against potential deadlock between userland and kernel iirc. Retrying means it can simple work. should there be some sort of retry count or timing period in which to decide to give up so that one doesn't retry forever? if yes, how might that be accomplished? ;) admittedly, i may have missed something in the ESysEINTR and ESysAgain portion since i'm a new babe with regards to signaling like that... but i just had to ask, ya know? ;) ___ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
