global regexps cause interp to stack overflow

[dgryski]

The following programs dies with stack overflow during the interp pass's "Update all global variables in the LLVM modules" loop, specifically the toLLVMValue call

package main

import (
	"regexp"
)

var foo = regexp.MustCompile("\r\n|[\n\r]")

func main() {
	println(foo.String())
}

A selection of the output follows:

2021/10/13 17:20:23 type main.foo PointerType(PointerType(%regexp.Regexp: StructType(%runtime._string: StructType(PointerType(IntegerType(8 bits)), IntegerType(32 bits)), PointerType(%regexp/syntax.Prog: StructType(StructType(PointerType(%regexp/syntax.Inst: StructType(IntegerType(8 bits), IntegerType(32 bits), IntegerType(32 bits), StructType(PointerType(IntegerType(32 bits)), IntegerType(32 bits), IntegerType(32 bits)))), IntegerType(32 bits), IntegerType(32 bits)), IntegerType(32 bits), IntegerType(32 bits))), PointerType(%regexp.onePassProg: StructType(StructType(PointerType(%regexp.onePassInst: StructType(%regexp/syntax.Inst: StructType(IntegerType(8 bits), IntegerType(32 bits), IntegerType(32 bits), StructType(PointerType(IntegerType(32 bits)), IntegerType(32 bits), IntegerType(32 bits))), StructType(PointerType(IntegerType(32 bits)), IntegerType(32 bits), IntegerType(32 bits)))), IntegerType(32 bits), IntegerType(32 bits)), IntegerType(32 bits), IntegerType(32 bits))), IntegerType(32 bits), IntegerType(32 bits), StructType(PointerType(%runtime._string: StructType(PointerType(IntegerType(8 bits)), IntegerType(32 bits))), IntegerType(32 bits), IntegerType(32 bits)), %runtime._string: StructType(PointerType(IntegerType(8 bits)), IntegerType(32 bits)), StructType(PointerType(IntegerType(8 bits)), IntegerType(32 bits), IntegerType(32 bits)), IntegerType(32 bits), IntegerType(32 bits), IntegerType(32 bits), IntegerType(32 bits), IntegerType(1 bits), IntegerType(8 bits), IntegerType(32 bits), IntegerType(1 bits))))
runtime: goroutine stack exceeds 1000000000-byte limit
runtime: sp=0xc02ac00348 stack=[0xc02ac00000, 0xc04ac00000]
fatal error: stack overflow

runtime stack:
runtime.throw({0x43a659e, 0x45fe0c0})
	/Users/dgryski/go/src/go.googlesource.com/go/src/runtime/panic.go:1198 +0x71
runtime.newstack()
	/Users/dgryski/go/src/go.googlesource.com/go/src/runtime/stack.go:1088 +0x5ac
runtime.morestack()
	/Users/dgryski/go/src/go.googlesource.com/go/src/runtime/asm_amd64.s:461 +0x8b

goroutine 14 [running]:
runtime.mapaccess2_fast32(0x4353200, 0xc009b211d0, 0x7c6)
	/Users/dgryski/go/src/go.googlesource.com/go/src/runtime/map_fast32.go:52 +0x18a fp=0xc02ac00358 sp=0xc02ac00350 pc=0x4014aea
github.com/tinygo-org/tinygo/interp.(*memoryView).get(0xc009b21170, 0x7c6)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:228 +0x9e fp=0xc02ac00460 sp=0xc02ac00358 pc=0x42c1c3e
github.com/tinygo-org/tinygo/interp.pointerValue.llvmValue(...)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:518
github.com/tinygo-org/tinygo/interp.pointerValue.toLLVMValue({0x0}, {0xc0068f4b00}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:526 +0x5b fp=0xc02ac00620 sp=0xc02ac00460 pc=0x42c383b
github.com/tinygo-org/tinygo/interp.rawValue.rawLLVMValue({{0xc0096d85a0, 0x7c6, 0xc02ac007a0}}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:802 +0x1d9 fp=0xc02ac00710 sp=0xc02ac00620 pc=0x42c4a39
github.com/tinygo-org/tinygo/interp.pointerValue.toLLVMValue({0x0}, {0xc0068f4a80}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:535 +0x1c5 fp=0xc02ac008d0 sp=0xc02ac00710 pc=0x42c39a5
github.com/tinygo-org/tinygo/interp.rawValue.rawLLVMValue({{0xc0096d85a0, 0x7c6, 0xc02ac00a50}}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:802 +0x1d9 fp=0xc02ac009c0 sp=0xc02ac008d0 pc=0x42c4a39
github.com/tinygo-org/tinygo/interp.pointerValue.toLLVMValue({0x0}, {0xc0068f4a00}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:535 +0x1c5 fp=0xc02ac00b80 sp=0xc02ac009c0 pc=0x42c39a5
github.com/tinygo-org/tinygo/interp.rawValue.rawLLVMValue({{0xc0096d85a0, 0x7c6, 0xc02ac00d00}}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:802 +0x1d9 fp=0xc02ac00c70 sp=0xc02ac00b80 pc=0x42c4a39
github.com/tinygo-org/tinygo/interp.pointerValue.toLLVMValue({0x0}, {0xc0068f4980}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:535 +0x1c5 fp=0xc02ac00e30 sp=0xc02ac00c70 pc=0x42c39a5
github.com/tinygo-org/tinygo/interp.rawValue.rawLLVMValue({{0xc0096d85a0, 0x7c6, 0x7f5a2252011c}}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:802 +0x1d9 fp=0xc02ac00f20 sp=0xc02ac00e30 pc=0x42c4a39
github.com/tinygo-org/tinygo/interp.pointerValue.toLLVMValue({0x0}, {0xc0068f4900}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:535 +0x1c5 fp=0xc02ac010e0 sp=0xc02ac00f20 pc=0x42c39a5
github.com/tinygo-org/tinygo/interp.rawValue.rawLLVMValue({{0xc0096d85a0, 0x7c6, 0xc02ac01260}}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:802 +0x1d9 fp=0xc02ac011d0 sp=0xc02ac010e0 pc=0x42c4a39
github.com/tinygo-org/tinygo/interp.pointerValue.toLLVMValue({0x0}, {0xc0068f4880}, 0xc009b21170)
	/Users/dgryski/go/src/github.com/tinygo-org/tinygo/interp/memory.go:535 +0x1c5 fp=0xc02ac01390 sp=0xc02ac011d0 pc=0x42c39a5
...

[dgryski]

So, the problem seems to be that when trying calling pointerValue.toLLVMValue(), the object is nil, and so

initializer, err := obj.buffer.asRawValue(mem.r).rawLLVMValue(mem)

is called, but rawValue.rawLLVMValue() decides to call

field, err := pointerValue{v.buf[i]}.toLLVMValue(llvm.Type{}, mem)

and we're back where we started.

[dkegel-fastly]

cf. #1830 and #1848

[dgryski]

Indeed. Fixed by #2001. Closing as duplicate.