diff --git a/include/vm/internals/opcode.h b/include/vm/internals/opcode.h
index 7dec73f..adc5d8b 100644
--- a/include/vm/internals/opcode.h
+++ b/include/vm/internals/opcode.h
@@ -7,7 +7,7 @@
 // Opcode handler descriptor
 typedef int (*opcode_handler)(fzl_vm_t *);
 
-extern char last_err[256];
+extern char last_err[512];
 extern size_t last_jmp_ip;
 extern size_t total_jmp_on_same;
 
diff --git a/src/vm/fzl_vm.c b/src/vm/fzl_vm.c
index b3d2d0c..6bc7184 100644
--- a/src/vm/fzl_vm.c
+++ b/src/vm/fzl_vm.c
@@ -12,7 +12,7 @@
 #include <vm/fzl_vm_reader.h>
 #include <vm/internals/opcode.h>
 
-char last_err[256];
+char last_err[512];
 char internal_error[256];
 size_t last_jmp_ip       = 0;
 size_t total_jmp_on_same = 0;
diff --git a/src/vm/fzl_vm_debug.c b/src/vm/fzl_vm_debug.c
index 0b3334e..54fe3eb 100644
--- a/src/vm/fzl_vm_debug.c
+++ b/src/vm/fzl_vm_debug.c
@@ -1,6 +1,7 @@
 #include <common/fzl_opcodes.h>
 #include <common/fzl_value.h>
 #include <stdbool.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <vm/fzl_vm.h>
 
diff --git a/src/vm/fzl_vm_reader.c b/src/vm/fzl_vm_reader.c
index 037c467..e49b486 100644
--- a/src/vm/fzl_vm_reader.c
+++ b/src/vm/fzl_vm_reader.c
@@ -8,7 +8,7 @@
 #include <vm/fzl_vm_reader.h>
 #include <vm/internals/reader.h>
 
-char reader_err[256];
+char reader_err[512];
 
 fzl_vm_reader_t *fzl_vm_mkreader(char *filepath)
 {
@@ -138,7 +138,12 @@ void fzl_vm_freereader(fzl_vm_reader_t *reader)
   }
 
   if (reader->extern_libs)
+  {
+    for (uint16_t i = 0; i < reader->extern_libs_count; i++)
+      free(reader->extern_libs[i]);
+
     free(reader->extern_libs);
+  }
 
   if (reader->extern_types)
   {
@@ -156,6 +161,8 @@ void fzl_vm_freereader(fzl_vm_reader_t *reader)
           if (fields[j].name)
             free(fields[j].name);
         }
+
+        free(fields);
       }
     }
 
@@ -163,7 +170,22 @@ void fzl_vm_freereader(fzl_vm_reader_t *reader)
   }
 
   if (reader->extern_fns)
+  {
+    for (uint16_t i = 0; i < reader->extern_fns_count; i++)
+    {
+      fzl_extern_fn_t *fn = &reader->extern_fns[i];
+      if (fn->used_name)
+        free(fn->used_name);
+
+      if (fn->symbol_name)
+        free(fn->symbol_name);
+
+      if (fn->args_count > 0)
+        free(fn->args);
+    }
+
     free(reader->extern_fns);
+  }
 
   if (reader->ops)
     free(reader->ops);
diff --git a/src/vm/main.c b/src/vm/main.c
index 2b55e0a..1cea6f8 100644
--- a/src/vm/main.c
+++ b/src/vm/main.c
@@ -155,6 +155,7 @@ int main(int argc, char **argv)
         printf("%sError%s: %s\n", FZL_CERROR, FZL_CRST, err);
 
       free(args);
+      fzl_vm_freereader(reader);
       fzl_freevm(vm);
       return -1;
     }
diff --git a/src/vm/reader/vm_rd_extern_fns.c b/src/vm/reader/vm_rd_extern_fns.c
index 1975eec..bb0f792 100644
--- a/src/vm/reader/vm_rd_extern_fns.c
+++ b/src/vm/reader/vm_rd_extern_fns.c
@@ -1,6 +1,11 @@
+#include <common/fzl_extern.h>
+#include <common/fzl_types.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
 #include <vm/fzl_vm_reader.h>
 #include <vm/internals/reader.h>
 
@@ -14,7 +19,216 @@ bool vm_rd_extern_fns(fzl_vm_reader_t *reader, FILE *fd)
   if (!fns_count)
     return true;
 
-  // TODO: fuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuuck
+  reader->extern_fns = malloc(sizeof(fzl_extern_fn_t) * fns_count);
+  if (!reader->extern_fns)
+  {
+    snprintf(internal_error, sizeof(internal_error), "out of memory");
+    return false;
+  }
+
+  memset(reader->extern_fns, 0, sizeof(fzl_extern_fn_t) * fns_count);
+
+  for (uint16_t i = 0; i < fns_count; i++)
+  {
+    fzl_extern_fn_t *fn = &reader->extern_fns[i];
+
+    uint16_t lib_slot;
+    if (!vm_rd_u16(fd, 1, &lib_slot))
+    {
+      snprintf(internal_error, sizeof(internal_error),
+               "failed to read fn #%u lib slot", i);
+      return false;
+    }
+
+    fn->lib_slot = lib_slot;
+
+    uint16_t used_name_sz;
+    if (!vm_rd_u16(fd, 1, &used_name_sz))
+    {
+      snprintf(internal_error, sizeof(internal_error),
+               "failed to read fn #%u used name size", i);
+      return false;
+    }
+
+    char used_name_buf[256];
+    memset(used_name_buf, 0, sizeof(used_name_buf));
+    if (!vm_rd_char(fd, used_name_sz, used_name_buf))
+    {
+      snprintf(internal_error, sizeof(internal_error),
+               "failed to read fn #%u used name", i);
+      return false;
+    }
+
+    char *val = malloc(sizeof(char) * used_name_sz + 1);
+    if (!val)
+    {
+      snprintf(internal_error, sizeof(internal_error),
+               "out of memory on fn #%u used name allocation", i);
+      return false;
+    }
+
+    memset(val, 0, sizeof(char) * used_name_sz + 1);
+    memcpy(val, used_name_buf, sizeof(char) * used_name_sz);
+    fn->used_name = val;
+
+    char has_symbol_name;
+    if (!vm_rd_char(fd, 1, &has_symbol_name))
+    {
+      snprintf(internal_error, sizeof(internal_error),
+               "failed to read fn #%u symbol name existing flag", i);
+      return false;
+    }
+
+    if ((bool)has_symbol_name)
+    {
+      if (!vm_rd_u16(fd, 1, &used_name_sz))
+      {
+        snprintf(internal_error, sizeof(internal_error),
+                 "failed to read fn #%u symbol name size", i);
+        return false;
+      }
+
+      if (!vm_rd_char(fd, used_name_sz, used_name_buf))
+      {
+        snprintf(internal_error, sizeof(internal_error),
+                 "failed to read fn #%u symbol name", i);
+        return false;
+      }
+
+      char *symval = malloc(sizeof(char) * used_name_sz + 1);
+      if (!symval)
+      {
+        snprintf(internal_error, sizeof(internal_error),
+                 "out of memory on fn #%u symbol name allocation", i);
+        return false;
+      }
+
+      memset(symval, 0, sizeof(char) * used_name_sz + 1);
+      memcpy(symval, used_name_buf, sizeof(char) * used_name_sz);
+      fn->symbol_name = symval;
+    }
+
+    char has_return;
+    if (!vm_rd_char(fd, 1, &has_return))
+    {
+      snprintf(internal_error, sizeof(internal_error),
+               "failed to read fn #%u return existing flag", i);
+      return false;
+    }
+
+    fn->has_return = (bool)has_return;
+    if ((bool)has_return)
+    {
+      char is_primitive;
+      if (!vm_rd_char(fd, 1, &is_primitive))
+      {
+        snprintf(internal_error, sizeof(internal_error),
+                 "failed to read fn #%u return type primitivity flag", i);
+        return false;
+      }
+
+      fn->ret_type.is_primitive = (bool)is_primitive;
+
+      if (is_primitive)
+      {
+        char primitive;
+        if (!vm_rd_char(fd, 1, &primitive))
+        {
+          snprintf(internal_error, sizeof(internal_error),
+                   "failed to read fn #%u return primitive", i);
+          return false;
+        }
+
+        fn->ret_type.primitive = (fzl_type_t)primitive;
+      }
+      else
+      {
+        uint16_t type_slot;
+        if (!vm_rd_u16(fd, 1, &type_slot))
+        {
+          snprintf(internal_error, sizeof(internal_error),
+                   "failed to read fn #%u return type slot", i);
+          return false;
+        }
+
+        fn->ret_type.type_slot = (size_t)type_slot;
+      }
+    }
+
+    uint16_t args_count;
+    if (!vm_rd_u16(fd, 1, &args_count))
+    {
+      snprintf(internal_error, sizeof(internal_error),
+               "failed to read fn #%u arguments count", i);
+      return false;
+    }
+
+    fn->args_count = (size_t)args_count;
+    if (args_count > 0)
+    {
+      fzl_extern_arg_t *args = malloc(sizeof(fzl_extern_arg_t) * args_count);
+      if (!args)
+      {
+        snprintf(internal_error, sizeof(internal_error),
+                 "out of memory on fn #%u arguments array allocation", i);
+        return false;
+      }
+
+      memset(args, 0, sizeof(fzl_extern_arg_t) * args_count);
+      fn->args = args;
+
+      for (uint16_t j = 0; j < args_count; j++)
+      {
+        fzl_extern_arg_t *arg = &args[j];
+
+        char arg_is_out;
+        if (!vm_rd_char(fd, 1, &arg_is_out))
+        {
+          snprintf(internal_error, sizeof(internal_error),
+                   "failed to read fn #%u arg #%u out flag", i, j);
+          return false;
+        }
+
+        arg->is_out = (bool)arg_is_out;
+
+        char arg_is_primitive;
+        if (!vm_rd_char(fd, 1, &arg_is_primitive))
+        {
+          snprintf(internal_error, sizeof(internal_error),
+                   "failed to read fn #%u arg #%u return type primitivity flag",
+                   i, j);
+          return false;
+        }
+
+        arg->type.is_primitive = (bool)arg_is_primitive;
+
+        if (arg_is_primitive)
+        {
+          char primitive;
+          if (!vm_rd_char(fd, 1, &primitive))
+          {
+            snprintf(internal_error, sizeof(internal_error),
+                     "failed to read fn #%u #%u return primitive", i, j);
+            return false;
+          }
+
+          arg->type.primitive = (fzl_type_t)primitive;
+        }
+        else
+        {
+          uint16_t type_slot;
+          if (!vm_rd_u16(fd, 1, &type_slot))
+          {
+            snprintf(internal_error, sizeof(internal_error),
+                     "failed to read fn #%u #%u return type slot", i, j);
+            return false;
+          }
+
+          arg->type.type_slot = (size_t)type_slot;
+        }
+      }
+    }
+  }
 
   return true;
 }
diff --git a/src/vm/reader/vm_rd_extern_libs.c b/src/vm/reader/vm_rd_extern_libs.c
index a6698db..66087d0 100644
--- a/src/vm/reader/vm_rd_extern_libs.c
+++ b/src/vm/reader/vm_rd_extern_libs.c
@@ -1,5 +1,6 @@
 #include <common/fzl_extern.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -25,14 +26,14 @@ bool vm_rd_extern_libs(fzl_vm_reader_t *reader, FILE *fd)
 
   memset(reader->extern_libs, 0, sizeof(char *) * libs_count);
 
-  bool ok          = false;
-  uint16_t name_sz = 0;
+  bool ok        = false;
+  size_t name_sz = 0;
   char name[256];
   for (uint16_t i = 0; i < libs_count; i++)
   {
     memset(name, 0, sizeof(name));
 
-    ok = vm_rd_u16(fd, 1, &name_sz);
+    ok = vm_rd_word(fd, 1, &name_sz);
     if (!ok || name_sz < 1)
     {
       snprintf(internal_error, sizeof(internal_error),
diff --git a/src/vm/reader/vm_rd_extern_types.c b/src/vm/reader/vm_rd_extern_types.c
index f1a1728..891c9a5 100644
--- a/src/vm/reader/vm_rd_extern_types.c
+++ b/src/vm/reader/vm_rd_extern_types.c
@@ -158,7 +158,7 @@ bool vm_rd_extern_types(fzl_vm_reader_t *reader, FILE *fd)
 
     for (uint16_t j = 0; j < fields_count; j++)
     {
-      fzl_extern_struct_field_t *f = &fields[i];
+      fzl_extern_struct_field_t *f = &fields[j];
 
       char has_name;
       if (!vm_rd_char(fd, 1, &has_name))
diff --git a/src/vm/reader/vm_rd_ops.c b/src/vm/reader/vm_rd_ops.c
index 30126bb..ed9ce8d 100644
--- a/src/vm/reader/vm_rd_ops.c
+++ b/src/vm/reader/vm_rd_ops.c
@@ -1,5 +1,6 @@
 #include <stdbool.h>
 #include <stddef.h>
+#include <stdio.h>
 #include <stdlib.h>
 #include <vm/internals/reader.h>
 
@@ -22,7 +23,7 @@ bool vm_rd_ops(fzl_vm_reader_t *reader, FILE *fd)
 
   for (size_t i = 0; i < ops_count; i++)
   {
-    size_t opcode;
+    size_t opcode = 0;
     if (!vm_rd_word(fd, 1, &opcode))
     {
       snprintf(internal_error, sizeof(internal_error),