mallctl() returns zeroes with jemalloc-prefix

[Antony Dovgal]

Hello all,

I'm trying to investigate the following issue:
jemalloc's mallctl() stops working when the lib is compiled with --with-jemalloc-prefix=<anything>
Does anyone have any idea how to fix this?

Here's a quick demonstration of the problem:

./configure --prefix=/local --with-jemalloc-prefix=test_ && make install

Modify the canonical example accordingly:
------------
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <jemalloc/jemalloc.h>

void
do_something(size_t i)
{

         // Leak some memory.
         malloc(i * 100);
}

int
main(int argc, char **argv)
{
         size_t i, sz;

         for (i = 0; i < 100; i++) {
                 do_something(i);

                 // Update the statistics cached by mallctl.
                 uint64_t epoch = 1;
                 sz = sizeof(epoch);
                 test_mallctl("epoch", &epoch, &sz, &epoch, sz); //PREFIX

                 // Get basic allocation statistics.  Take care to check for
                 // errors, since --enable-stats must have been specified at
                 // build time for these statistics to be available.
                 size_t sz, allocated, active, mapped;
                 sz = sizeof(size_t);
                 if (test_mallctl("stats.allocated", &allocated, &sz, NULL, 0) == 0 //PREFIX
                     && test_mallctl("stats.active", &active, &sz, NULL, 0) == 0 //PREFIX
                     && test_mallctl("stats.mapped", &mapped, &sz, NULL, 0) == 0) { //PREFIX
                         fprintf(stderr,
                             "Current allocated/active/mapped: %zu/%zu/%zu\n",
                             allocated, active, mapped);
                 }
         }

         return (0);
}
------------

And the output of this code looks like this:
...
Current allocated/active/mapped: 0/0/4194304
Current allocated/active/mapped: 0/0/4194304
Current allocated/active/mapped: 0/0/4194304
Current allocated/active/mapped: 0/0/4194304
...

The ctl tree looks ok and the entries are indeed found, but for some reason they are empty (well, except for stats.mapped).
And yes, everything works fine as long as I don't use any prefix.

-- 
Wbr,
Antony Dovgal
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