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go/analysis/passes/printf: fix false negative with nested pointers

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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.

This change was originally made to cmd/vet as
https://go-review.googlesource.com/c/147997.

Updates #27672.

Change-Id: I65944cf355baedb4578af57046e2bbfd3fe6a9dc
Reviewed-on: https://go-review.googlesource.com/c/149319
Reviewed-by: Michael Matloob <matloob@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
This commit is contained in:
Alan Donovan 2018-11-13 13:28:57 -05:00
parent c921186869
commit 0a8e63141f
2 changed files with 16 additions and 4 deletions
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10
go/analysis/passes/printf/testdata/src/a/a.go vendored
View File

@ -237,7 +237,7 @@ 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) // want `Printf format %x has arg recursiveStruct1V\.next of wrong type \*a\.RecursiveStruct2`
Printf("%p %x", recursiveSliceV, recursiveSliceV)
Printf("%p %x", recursiveMapV, recursiveMapV)
// Special handling for Log.
@ -678,6 +678,14 @@ func PointersToCompoundTypes() {
intMap := map[int]int{3: 4}
fmt.Printf("%s", &intMap) // want `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"}}) // want `Printf format %s has arg T1{&T2{.x.}} of wrong type a\.T1`
}
// Printf wrappers from external package

10
go/analysis/passes/printf/types.go
View File

@ -108,9 +108,13 @@ func matchArgTypeInternal(pass *analysis.Pass, t printfArgType, typ types.Type,
// 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 matchArgTypeInternal(pass, t, under, arg, inProgress)
case *types.Struct: