C API: wasm_module_imports leaks memory

[tudor]

wasmer 2.0.0

To reproduce, compile the following program with clang's (or gcc's) address sanitizer. /tmp/e2.wasm has 2 imports.

C code:

#include <wasm.h>
#include <stdio.h>

int main(int argc, char* argv[]) {
    wasm_engine_t* engine = wasm_engine_new();
    wasm_store_t* store = wasm_store_new(engine);

    FILE* fp = fopen("/tmp/e2.wasm", "rb");
    fseek(fp, 0, SEEK_END);
    size_t size = ftell(fp);
    fseek(fp, 0, SEEK_SET);

    wasm_byte_vec_t data;
    wasm_byte_vec_new_uninitialized(&data, size);
    fread(data.data, size, 1, fp);
    fclose(fp);

    wasm_module_t* module = wasm_module_new(store, &data);

    wasm_importtype_vec_t importTypes;
    wasm_module_imports(module, &importTypes);

    wasm_importtype_vec_delete(&importTypes);
    wasm_module_delete(module);
    wasm_byte_vec_delete(&data);
    wasm_store_delete(store);
    wasm_engine_delete(engine);
}

Compilation line:

clang-12 -g -fsanitize=address -o /tmp/a /tmp/a.c -lwasmer

Errors:

=================================================================
==10573==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 8 byte(s) in 1 object(s) allocated from:
    #0 0x49669d in malloc (/tmp/a+0x49669d)
    #1 0x7f27ef81e392 in _$LT$alloc..vec..Vec$LT$T$GT$$u20$as$u20$alloc..vec..spec_from_iter..SpecFromIter$LT$T$C$I$GT$$GT$::from_iter::h0a4e053b7d1f2fc8 (/usr/local/lib/libwasmer.so+0x92392)

Objects leaked above:
0x602000000d30 (8 bytes)

Indirect leak of 1 byte(s) in 1 object(s) allocated from:
    #0 0x49669d in malloc (/tmp/a+0x49669d)
    #1 0x7f27ef81fb47 in _$LT$core..iter..adapters..map..Map$LT$I$C$F$GT$$u20$as$u20$core..iter..traits..iterator..Iterator$GT$::fold::hd77c1645fbe20366 (/usr/local/lib/libwasmer.so+0x93b47)

Objects leaked above:
0x602000000d50 (1 bytes)

SUMMARY: AddressSanitizer: 9 byte(s) leaked in 2 allocation(s).

C code compiled to wasm using wasi-sdk:

__attribute__((import_module("foo"), import_name("foo"))) void foo(void);
int main() {
    foo();
}

Resulting wasm:

(module
  (type (;0;) (func (param i32)))
  (type (;1;) (func))
  (type (;2;) (func (result i32)))
  (import "wasi_snapshot_preview1" "proc_exit" (func $__wasi_proc_exit (type 0)))
  (import "foo" "foo" (func $foo (type 1)))
  (func $__wasm_call_ctors (type 1))
  (func $_start (type 1)
    (local i32)
    call $__wasm_call_ctors
    call $__original_main
    local.set 0
    call $__wasm_call_dtors
    block  ;; label = @1
      local.get 0
      i32.eqz
      br_if 0 (;@1;)
      local.get 0
      call $__wasi_proc_exit
      unreachable
    end)
  (func $__original_main (type 2) (result i32)
    (local i32)
    i32.const 0
    local.set 0
    call $foo
    local.get 0
    return)
  (func $dummy (type 1))
  (func $__wasm_call_dtors (type 1)
    call $dummy
    call $dummy)
  (table (;0;) 1 1 funcref)
  (memory (;0;) 2)
  (global (;0;) (mut i32) (i32.const 66560))
  (export "memory" (memory 0))
  (export "_start" (func $_start)))

[tudor]

Commenting out various parts of the code does indicate that the leak comes from wasm_module_imports

[syrusakbary]

Thanks for the detailed report @tudor

[wchaudry]

@syrusakbary to look into a blocking PR that has not been merged.