give the possibility to redirect the stderr to nullptr

[mynickmynick]

In the actual implementation the stderr is not redirectable to nullptr because in
user.c
qh_new_qhull
line 145
if(!errfile){
errfile= stderr;
}

and
same in user_r.c
line 133
if(!errfile){
errfile= stderr;
}

I think that is not correct.
As a matter of facts I am using qhull to implement a segmentation so I have to apply subsequently many times also to small sets where I happen to get often errors by qhull and so my stderr is flood with unwanted verbouse errors, while I just would like to catch the exit error code to handle it accordingly

But in general the user should be able to redirect stderr to null as it happens standard with most tools

If I delete these lines of code
//if(!errfile){
// errfile= stderr;
//}
and I set errfile=nullptr
then I get other errors by the called error log output functions

I wonder if it is sufficient to add code like this

if (!fp)
return;

at the beginning of all error log output functions (which seem to be many... are there a few that collect all of it?)

[themightyoarfish]

For reference:

qhull/src/libqhull/user.c

Line 145 in c2ef220

if(!errfile){

What is the reason for that code existing? Limits usefulness of qhull for wrapping tools. Is the intended way to go about this for the user to pass their own file pointer and direct it into the void?

[cbbarber]

Qhull is designed for error handling. All computations are done in floating point arithmetic which is inherently imprecise. The geometric computations are used to make topological decisions. All kinds of errors can occur. In short it is important to track and manage errors.

Qhull offers multiple options for output (see user_r.h an user_r.c User definable options)

All output goes through qh_fprintf with a location ID. You can define your own qh_fprintf in userprintf_r.c and use the results as needed. Option 'Ta' annotates output with the location ID.

Rewrite qh_printhelp* in user_r.c (the long descriptive error messages), These messages are shortened if 'qh_QUICKhelp' is set in user_r..h. In addition, qh_QUICKhelp reduces output elsewhere.

Rewrite qh_errexit and qh_errprint in user_r.c to define your own error handling.

[Nekto89]

I had to put all qhull (7.3.2) functionality under mutex on my side because on macOS something breaks if I pass /dev/null to qhull. Each thread has it's own FILE* and qhull handle. I saw that qhull uses fflush(NULL) in some places. Maybe it's not threadsafe?