Commit e06a64a4 authored by Matthew Dempsky's avatar Matthew Dempsky

cmd/compile/internal/syntax: fix source buffer refilling

The previous code seems to have an off-by-1 in it somewhere, the
consequence being that we didn't properly preserve all of the old
buffer contents that we intended to.

After spending a while looking at the existing window-shifting logic,
I wasn't able to understand exactly how it was supposed to work or
where the issue was, so I rewrote it to be (at least IMO) more
obviously correct.

Fixes #21938.

Change-Id: I1ed7bbc1e1751a52ab5f7cf0411ae289586dc345
Reviewed-on: https://go-review.googlesource.com/64830
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: 's avatarRobert Griesemer <gri@golang.org>
parent a53e8539
...@@ -7,6 +7,7 @@ package syntax ...@@ -7,6 +7,7 @@ package syntax
import ( import (
"fmt" "fmt"
"os" "os"
"strings"
"testing" "testing"
) )
...@@ -367,3 +368,15 @@ func TestScanErrors(t *testing.T) { ...@@ -367,3 +368,15 @@ func TestScanErrors(t *testing.T) {
} }
} }
} }
func TestIssue21938(t *testing.T) {
s := "/*" + strings.Repeat(" ", 4089) + "*/ .5"
var got scanner
got.init(strings.NewReader(s), nil, nil)
got.next()
if got.tok != _Literal || got.lit != ".5" {
t.Errorf("got %s %q; want %s %q", got.tok, got.lit, _Literal, ".5")
}
}
...@@ -164,11 +164,12 @@ func (s *source) fill() { ...@@ -164,11 +164,12 @@ func (s *source) fill() {
s.lit = append(s.lit, s.buf[s.suf:s.r0]...) s.lit = append(s.lit, s.buf[s.suf:s.r0]...)
s.suf = 1 // == s.r0 after slide below s.suf = 1 // == s.r0 after slide below
} }
s.offs += s.r0 - 1 n := s.r0 - 1
r := s.r - s.r0 + 1 // last read char plus one byte copy(s.buf[:], s.buf[n:s.w])
s.w = r + copy(s.buf[r:], s.buf[s.r:s.w]) s.offs += n
s.r = r s.r0 = 1 // eqv: s.r0 -= n
s.r0 = 1 s.r -= n
s.w -= n
} }
// read more data: try a limited number of times // read more data: try a limited number of times
......
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