From b76c61051faaf0baf3215e6f811003d98639b702 Mon Sep 17 00:00:00 2001 From: Ian Lance Taylor Date: Fri, 29 Jan 2016 12:39:47 -0800 Subject: [PATCH] bind: pass &v[0] in direct call to C In Go 1.6, the cgo checking rules are more precise when they see an address operation as an argument to the C function. When you pass &v[0] to a C function, the cgo check just verifies that v itself does not contain any pointers. When you write `p := &v[0]` and then pass p to the C function, the cgo check is conservative: it verifies that the entire memory block to which p points does not contain any pointers. When the bind function is called by code that passes a slice that is part of a larger struct, this means that the cgo check will look at the entire larger struct, not just the slice. This can cause a surprising run time failure. Avoid this problem by rewriting the code slightly to pass &v[0] in the call to the C function itself. In particular this fixes the tests of github.com/jmoiron/sqlx when using Go 1.6. --- sqlite3.go | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/sqlite3.go b/sqlite3.go index f79ef2d..eae71ab 100644 --- a/sqlite3.go +++ b/sqlite3.go @@ -814,11 +814,11 @@ func (s *SQLiteStmt) bind(args []driver.Value) error { case float64: rv = C.sqlite3_bind_double(s.s, n, C.double(v)) case []byte: - var p *byte - if len(v) > 0 { - p = &v[0] + if len(v) == 0 { + rv = C._sqlite3_bind_blob(s.s, n, nil, 0) + } else { + rv = C._sqlite3_bind_blob(s.s, n, unsafe.Pointer(&v[0]), C.int(len(v))) } - rv = C._sqlite3_bind_blob(s.s, n, unsafe.Pointer(p), C.int(len(v))) case time.Time: b := []byte(v.Format(SQLiteTimestampFormats[0])) rv = C._sqlite3_bind_text(s.s, n, (*C.char)(unsafe.Pointer(&b[0])), C.int(len(b)))