sys_errlist was removed for a reason. Creating a fake sys_errlist on Solaris will mean the libhadoop.so will need to be tied a specific build (kernel/include pairing) and therefore limits upward mobility/compatibility. That doesn’t seem like a very good idea.
IMO, switching to strerror_r is much preferred, since other than the brain-dead GNU libc version, is highly portable and should work regardless of the kernel or OS in place. On Dec 11, 2014, at 5:20 AM, malcolm <malcolm.kaval...@oracle.com> wrote: > FYI, there are a couple more files that reference sys_errlist directly (not > just terror within exception.c) , but also hdfs_http_client.c and NativeiO.c > > On 12/11/2014 07:38 AM, malcolm wrote: >> Hi Colin, >> >> Exactly, as you noticed, the problem is the thread-local buffer needed to >> return from terror. >> Currently, terror just returns a static string from an array, this is fast, >> simple and error-proof. >> >> In order to use strerror_r inside terror, would require allocating a buffer >> inside terror and depend on the caller to free the buffer after using it, >> or to pass a buffer to terrror (which is basically the same as strerror_r, >> rendering terror redundant). >> Both cases require modification outside terror itself, as far as I can tell, >> no simple fix. Unless you have an alternative which I haven't thought of ? >> >> As far as I can tell, we have two choices: >> >> 1. Remove terror and replace calls with strerror_r, passing a buffer from >> the callee. >> Advantage: a more modern portable interface. >> Disadvantage: All calls to terror need to be modified, though all seem to >> be in a few files as far as I can tell. >> >> 2. Adding a sys_errlist array (ifdeffed for Solaris) >> Advantage: no change to any calls to terror >> Disadvantage: 2 additional files added to source tree (.c and .h) and >> some minor ifdefs only used for Solaris. >> >> I think it is more a question of style than anything else, so I leave you to >> make the call. >> >> Thanks for your patience, >> Malcolm >> >> >> >> >> >> On 12/10/2014 09:54 PM, Colin McCabe wrote: >>> On Wed, Dec 10, 2014 at 2:31 AM, malcolm <malcolm.kaval...@oracle.com> >>> wrote: >>>> Hi Colin, >>>> >>>> Thanks for the hints around JIRAs. >>>> >>>> You are correct errno still exists, however sys_errlist does not. >>>> >>>> Hadoop uses a function terror (defined in exception.c) which indexes >>>> sys_errlist by errno to return the error message from the array. This >>>> function is called 26 times in various places (in 2.2) >>>> >>>> Originally, I thought to replace all calls to terror with strerror, but >>>> there can be issues with multi-threading (it returns a buffer which can be >>>> overwritten), so it seemed simpler just to recreate the sys_errlist message >>>> array. >>>> >>>> There is also a multi-threaded version strerror_r where you pass the buffer >>>> as a parameter, but this would necessitate changing every call to terror >>>> with mutiple lines of code. >>> Why don't you just use strerror_r inside terror()? >>> >>> I wrote that code originally. The reason I didn't want to use >>> strerror_r there is because GNU libc provides a non-POSIX definition >>> of strerror_r, and forcing it to use the POSIX one is a pain. But you >>> can do it. You also will require a thread-local buffer to hold the >>> return from strerror_r, since it is not guaranteed to be static >>> (although in practice it is 99% of the time-- another annoyance with >>> the API). >>> >>> >> >
