You should be able to pass cstring type variable to pointer type parameter
without cast. cstring is same to `char*` in C and it is a pointer to char.
var val = duckdb_value_varchar(addr(res), col.csize_t, row.csize_t)
free(addr(val))
Run
This code is wrong because you are passing the address of a variable to free.
You have to pass `val` to `free`. Changing `free` 's parameter from `pointer`
to `ptr cstring` does not fix the problem. Don't you get any runtime error in
`free(addr(val))`?
It should be like this as Araq said:
proc free(p: pointer) {.importc: "free", header: "<stdlib.h>".}
# duckdb_value_varchar returns cstring
var val = duckdb_value_varchar(addr(res), col.csize_t, row.csize_t)
echo val
free(val)
Run
It seems writing C library binding without knowing C is dangrous as C compiler
cannot checks some errors like this. I think you need to learn C language. When
you learn about a C library, you need to read documents written for C
programmer. Most of C library bindings for Nim only provides Nim example codes,
don't provide detailed documents of each procedures for Nim programmer. When
you got a bug in C library, you need to read C code to find it and have to
write a minimum and runnable C code that reproduce the bug when you report
about the bug to library auther.
