struct ZHRegexCtx *targ = RedisModule_Alloc(sizeof(struct ZHRegexCtx));
*targ = { .ctx = ... };

struct ZHRegexCtx *targ = RedisModule_Alloc(sizeof(struct ZHRegexCtx));
    struct ZHRegexCtx rarg = (struct ZHRegexCtx) {
     ...
    };
    *targ = rarg;

    gcc -Wall -g -fPIC -lc -lm -Og -std=gnu99 -I.   -c -o module.o module.c
    module.c: In function ‘ZHRegex_RedisCommand’:
    module.c:422:11: error: assignment of read-only location ‘*targ’
         *targ = rarg;
               ^

struct ZHRegexCtx *targ = RedisModule_Alloc(sizeof(struct ZHRegexCtx));
struct ZHRegexCtx rarg = { ... };
memcpy(targ, &rarg, sizeof(struct ZHRegexCtx));