zweak_map leaks ~400 bytes per entry, even after removal

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Each zweak_map_set() leaks about 400 bytes that are never reclaimed, even after the entry is removed. zweak_map_size() returns 0 and FUGC_VERBOSE shows a flat live heap, but RSS grows without bound. The same thing happens when keys just die instead of being removed. Churning zweak_new() or zgc_finq_alloc() the same way doesn't leak.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdfil.h>

int main(void) {
    zweak_map *m = zweak_map_new();
    for (int round = 0; round < 8; round++) {
        for (int i = 0; i < 100000; i++) {
            void *key = malloc(64);
            zweak_map_set(m, key, key);
            zweak_map_set(m, key, NULL);
        }
        zgc_request_and_wait();
        char line[256];
        FILE *f = fopen("/proc/self/status", "r");
        while (fgets(line, sizeof line, f))
            if (!strncmp(line, "VmRSS:", 6)) printf("round %d: size=%zu %s", round, zweak_map_size(m), line);
        fclose(f);
    }
}

Output on Fil-C 0.686 (optfil, linux aarch64):

round 0: size=0 VmRSS: 63540 kB
round 7: size=0 VmRSS: 351456 kB

Found while porting Ruby 4.0 to Fil-C, which used a zweak_map per allocated object.

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pizlonator8d ago

Sounds bad! Will look