Crashes under component adapter due to duplicate imports

[erikrose]

Under common circumstances, the SDK emits builds containing duplicate imports. While this may or may not cause problems for core-warm modules, it does cause fatal errors during warming when running under the component adapter. (The Component spec says "All import names are required to be unique…", so validation gets grumpy.)

Under TinyGo, all is well. This happens only in standard Go.

We can trigger it simply by importing fmt:

package main

import (
	"fmt"
)

func main() {
	fmt.Println("Boo.")
}

This simple Hello World yields a duplicate import of fd_write:

(module
  (@custom "go:buildid" (before first) "\ff Go build ID: \22ZAI6HtN-4zG0VVqmMtgC/rfEJODF44cJvsrHdxcKc/B64BrDsnqrpbbNq-uDKP/AWH8AG7tT8ZUOccLYjcx\22\0a \ff")
  (type (;0;) (func (param i32) (result i32)))
  (type (;1;) (func (result i32)))
  (type (;2;) (func (param i32)))
  (type (;3;) (func (param i32 i32) (result i32)))
  (type (;4;) (func (param i32 i64 i32) (result i32)))
  (type (;5;) (func (param i32 i32 i32 i32) (result i32)))
  (type (;6;) (func (param i32 i32 i32) (result i32)))
  (type (;7;) (func (param i64 i64 i64 i64) (result i64)))
  (type (;8;) (func (param i64 i64 i64) (result i64)))
  (type (;9;) (func (param i64) (result i64)))
  (type (;10;) (func (result i64)))
  (type (;11;) (func))
  (type (;12;) (func (param i64 i64) (result i64)))
  (type (;13;) (func (param f64) (result i64)))
  (import "wasi_snapshot_preview1" "sched_yield" (func (;0;) (type 1)))
  (import "wasi_snapshot_preview1" "proc_exit" (func (;1;) (type 2)))
  (import "wasi_snapshot_preview1" "args_get" (func (;2;) (type 3)))
  (import "wasi_snapshot_preview1" "args_sizes_get" (func (;3;) (type 3)))
  (import "wasi_snapshot_preview1" "clock_time_get" (func (;4;) (type 4)))
  (import "wasi_snapshot_preview1" "environ_get" (func (;5;) (type 3)))
  (import "wasi_snapshot_preview1" "environ_sizes_get" (func (;6;) (type 3)))
  (import "wasi_snapshot_preview1" "fd_write" (func (;7;) (type 5)))
  (import "wasi_snapshot_preview1" "random_get" (func (;8;) (type 3)))
  (import "wasi_snapshot_preview1" "poll_oneoff" (func (;9;) (type 5)))
  (import "wasi_snapshot_preview1" "fd_close" (func (;10;) (type 0)))
  (import "wasi_snapshot_preview1" "fd_write" (func (;11;) (type 5)))
  (import "wasi_snapshot_preview1" "fd_fdstat_get" (func (;12;) (type 3)))
  (import "wasi_snapshot_preview1" "fd_fdstat_set_flags" (func (;13;) (type 3)))
  (import "wasi_snapshot_preview1" "fd_prestat_get" (func (;14;) (type 3)))
  (import "wasi_snapshot_preview1" "fd_prestat_dir_name" (func (;15;) (type 6)))
  (table (;0;) 5707 funcref)

For comparison, compiling an empty main() (and thus no fmt import) emits only 1 fd_write:

(module
  (@custom "go:buildid" (before first) "\ff Go build ID: \22oJjh20Vd5HLdjwBLqkiv/3cWfLYIpQjXR-C7uRXx-/irQbKsKoC6gLX3wKK44S/XmL4TBTGUnyXE0hCNQd1\22\0a \ff")
  (type (;0;) (func (param i32) (result i32)))
  (type (;1;) (func (result i32)))
  (type (;2;) (func (param i32)))
  (type (;3;) (func (param i32 i32) (result i32)))
  (type (;4;) (func (param i32 i64 i32) (result i32)))
  (type (;5;) (func (param i32 i32 i32 i32) (result i32)))
  (type (;6;) (func (param i64 i64 i64) (result i64)))
  (type (;7;) (func (param i32 i32 i32) (result i32)))
  (type (;8;) (func (param i64) (result i64)))
  (type (;9;) (func (result i64)))
  (type (;10;) (func))
  (type (;11;) (func (param i64 i64) (result i64)))
  (type (;12;) (func (param f64) (result i64)))
  (import "wasi_snapshot_preview1" "sched_yield" (func (;0;) (type 1)))
  (import "wasi_snapshot_preview1" "proc_exit" (func (;1;) (type 2)))
  (import "wasi_snapshot_preview1" "args_get" (func (;2;) (type 3)))
  (import "wasi_snapshot_preview1" "args_sizes_get" (func (;3;) (type 3)))
  (import "wasi_snapshot_preview1" "clock_time_get" (func (;4;) (type 4)))
  (import "wasi_snapshot_preview1" "environ_get" (func (;5;) (type 3)))
  (import "wasi_snapshot_preview1" "environ_sizes_get" (func (;6;) (type 3)))
  (import "wasi_snapshot_preview1" "fd_write" (func (;7;) (type 5)))
  (import "wasi_snapshot_preview1" "random_get" (func (;8;) (type 3)))
  (import "wasi_snapshot_preview1" "poll_oneoff" (func (;9;) (type 5)))
  (table (;0;) 5184 funcref)

fd_write is not unique in this respect, though it is the most common. Several other duplicates occur in the wild as well.