From 4d913b332cf161df7c4f3717c602d491d7ac01dd Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Daniel=20Mart=C3=AD?= Date: Tue, 6 Nov 2018 21:35:23 +0000 Subject: [PATCH] cmd/vet: fix printf false negative with nested pointers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Pointers to compound objects (structs, slices, arrays, maps) are only followed by fmt if the pointer is at the top level of an argument. This is to minimise the chances of fmt running into loops. However, vet did not follow this rule. It likely doesn't help that fmt does not document that restriction well, which is being tracked in #28625. Updates #27672. Change-Id: Ie9bbd9b974eda5ab9a285986d207ef92fca4453e Reviewed-on: https://go-review.googlesource.com/c/147997 Run-TryBot: Daniel Martí TryBot-Result: Gobot Gobot Reviewed-by: Alan Donovan --- src/cmd/vet/testdata/print.go | 10 +++++++++- src/cmd/vet/types.go | 10 +++++++--- 2 files changed, 16 insertions(+), 4 deletions(-) diff --git a/src/cmd/vet/testdata/print.go b/src/cmd/vet/testdata/print.go index b2289bc2acc..994902d01da 100644 --- a/src/cmd/vet/testdata/print.go +++ b/src/cmd/vet/testdata/print.go @@ -234,7 +234,7 @@ func PrintfTests() { Printf("%T", someFunction) // ok: maybe someone wants to see the type // Bug: used to recur forever. Printf("%p %x", recursiveStructV, recursiveStructV.next) - Printf("%p %x", recursiveStruct1V, recursiveStruct1V.next) + Printf("%p %x", recursiveStruct1V, recursiveStruct1V.next) // ERROR "Printf format %x has arg recursiveStruct1V\.next of wrong type \*testdata\.RecursiveStruct2" Printf("%p %x", recursiveSliceV, recursiveSliceV) Printf("%p %x", recursiveMapV, recursiveMapV) // Special handling for Log. @@ -670,4 +670,12 @@ func PointersToCompoundTypes() { intMap := map[int]int{3: 4} fmt.Printf("%s", &intMap) // ERROR "Printf format %s has arg &intMap of wrong type \*map\[int\]int" + + type T2 struct { + X string + } + type T1 struct { + X *T2 + } + fmt.Printf("%s\n", T1{&T2{"x"}}) // ERROR "Printf format %s has arg T1{&T2{.x.}} of wrong type testdata\.T1" } diff --git a/src/cmd/vet/types.go b/src/cmd/vet/types.go index 78823aed979..8cb0e8e77db 100644 --- a/src/cmd/vet/types.go +++ b/src/cmd/vet/types.go @@ -227,9 +227,13 @@ func (f *File) matchArgTypeInternal(t printfArgType, typ types.Type, arg ast.Exp // Check whether the rest can print pointers. return t&argPointer != 0 } - // If it's a pointer to a struct, array, slice, or map, that's - // equivalent in our analysis to whether we can print the type - // being pointed to. + // If it's a top-level pointer to a struct, array, slice, or + // map, that's equivalent in our analysis to whether we can + // print the type being pointed to. Pointers in nested levels + // are not supported to minimize fmt running into loops. + if len(inProgress) > 1 { + return false + } return f.matchArgTypeInternal(t, under, arg, inProgress) case *types.Struct: