net/http: panic when a nil HandlerFunc is passed to http.HandleFunc #24297
Comments
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Please finish filling in the issue template, specifically what did you see
when you ran your example.
What would be the ideal resolution to this bug for you?
…On 7 March 2018 at 23:22, wangsong93 ***@***.***> wrote:
Please answer these questions before submitting your issue. Thanks!
What version of Go are you using (go version)?
1.9.2
Does this issue reproduce with the latest release?
yes
What operating system and processor architecture are you using (go env)?
amd64 linux
What did you do?
package main
import "net/http"
func main() {
http.HandleFunc("/", nil)
http.ListenAndServe(":8080", nil)
}
What did you expect to see?
when I go run this file, the nil error appears not in compilation time but
in run time. The reason is that http.Handler(http.HandlerFunc(nil)) == nil
is false. BUT use reflect we can know the value of
http.Handler(http.HandlerFunc(nil)) is nil, so the error should be
stopped in compilation time by fix Handle function.
What did you see instead?
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namusyaka
changed the title
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I guess he would like to say that it is a matter of panic occurring after the And it is possible to generate a more descriptive panic by actually checking whether it is nil at the timing when diff --git a/src/net/http/server.go b/src/net/http/server.go
index a7ba753bf5..04a0444140 100644
--- a/src/net/http/server.go
+++ b/src/net/http/server.go
@@ -2358,6 +2358,9 @@ func (mux *ServeMux) Handle(pattern string, handler Handler) {
// HandleFunc registers the handler function for the given pattern.
func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Request)) {
+ if handler == nil {
+ panic("net/http: handler must not be nil")
+ }
mux.Handle(pattern, HandlerFunc(handler))
}
/cc @bradfitz @tombergan |
andybons
changed the title
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We won’t be able to catch this at compile time. @namusyaka’s fix seems reasonable unless I’m missing something. |
andybons
added
help wanted
NeedsFix
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I mean how to reproduce the panic in following code even if the 2nd parameter is nil func (mux *ServeMux) Handle(pattern string, handler Handler) {
mux.mu.Lock()
defer mux.mu.Unlock()
if pattern == "" {
panic("http: invalid pattern " + pattern)
}
// if reflect.ValueOf(handler).IsNil() { // this can be a solution
if handler == nil {
panic("http: nil handler")
}
if mux.m[pattern].explicit {
panic("http: multiple registrations for " + pattern)
} |
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I'm going to send a CL about this problem in a few days. |
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@wangsong93 I don't think it is a solution about the issue. Since it is called on every request, it should not be an essential solution. |
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@namusyaka yes, your solution is better and I agree. My solution is just used to verify my idea. Nil parameters should be stopped as earlier as possible. |
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Change https://golang.org/cl/99575 mentions this issue: |
Please answer these questions before submitting your issue. Thanks!
What version of Go are you using (
go version)?1.9.2
Does this issue reproduce with the latest release?
yes
What operating system and processor architecture are you using (
go env)?amd64 linux
What did you do?
What did you expect to see?
when I go run this file, the nil error appears not in compilation time but in run time. The reason is that
http.Handler(http.HandlerFunc(nil)) == nilis false. BUT use reflect we can know the value ofhttp.Handler(http.HandlerFunc(nil))is nil, so the error should be stopped in compilation time by fix Handle function.What did you see instead?
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