Hi Ian,
> This patch to the Go frontend changes value methods to always check
> that the pointer they are passed is not nil. We already dereference
> the pointer to copy the value, but if the method does not use the
> value then the pointer dereference may be optimized away. Do an
> explicit nil check so that we get the panic that is required by the
> language. This fixes https://golang.org/issue/19806. I added a test
> case to gcc/testsuite/go.go-torture/execute to test this at various
> optimization levels; the test used to fail at -O1 and above.
> Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu. Committed
> to mainline.
>
> Ian
>
> 2018-01-31 Ian Lance Taylor <[email protected]>
>
> * go.go-torture/execute/printnil.go: New test.
the new test FAILs on Solaris 10, sparc and x86 (only, 11 is fine) at
all optimization levels:
+FAIL: go.go-torture/execute/printnil.go execution, -O0
+FAIL: go.go-torture/execute/printnil.go execution, -O1
+FAIL: go.go-torture/execute/printnil.go execution, -O2
+FAIL: go.go-torture/execute/printnil.go execution, -O2 -fbounds-check
+FAIL: go.go-torture/execute/printnil.go execution, -O2 -fomit-frame-pointer
-finline-functions
+FAIL: go.go-torture/execute/printnil.go execution, -O2 -fomit-frame-pointer
-finline-functions -funroll-loops
+FAIL: go.go-torture/execute/printnil.go execution, -O3 -g
+FAIL: go.go-torture/execute/printnil.go execution, -Os
Don't know yet what the difference is, though. Here's the failing
stacktrace:
#0 runtime.gopanic (e=...)
at /vol/gcc/src/hg/trunk/solaris/libgo/go/runtime/panic.go:423
#1 0xfffffd7ffe492705 in runtime_panicstring (
s=s@entry=0xfffffd7ffe98d425 "nil pointer dereference")
at /vol/gcc/src/hg/trunk/solaris/libgo/runtime/panic.c:38
#2 0xfffffd7ffe49168b in __go_runtime_error (i=<optimized out>)
at /vol/gcc/src/hg/trunk/solaris/libgo/runtime/go-runtime-error.c:76
#3 0x0000000000402a97 in main.MyType.String ()
at
/vol/gcc/src/hg/trunk/solaris/gcc/testsuite/go.go-torture/execute/printnil.go:11
#4 0xfffffd7ffe5d15f5 in fmt.pp.handleMethods (p=p@entry=0xc4200a2180,
verb=verb@entry=115)
at /vol/gcc/src/hg/trunk/solaris/libgo/go/fmt/print.go:603
#5 0xfffffd7ffe5d0e2b in fmt.pp.printArg (p=p@entry=0xc4200a2180, arg=...,
verb=115) at /vol/gcc/src/hg/trunk/solaris/libgo/go/fmt/print.go:686
#6 0xfffffd7ffe5d2794 in fmt.pp.doPrintf (p=p@entry=0xc4200a2180, format=...,
a=...) at /vol/gcc/src/hg/trunk/solaris/libgo/go/fmt/print.go:1003
#7 0xfffffd7ffe5d2cd6 in fmt.Sprintf (format=..., a=...)
at /vol/gcc/src/hg/trunk/solaris/libgo/go/fmt/print.go:203
#8 0x0000000000402b73 in main.main ()
at
/vol/gcc/src/hg/trunk/solaris/gcc/testsuite/go.go-torture/execute/printnil.go:16
At first I thought this might be related to Solaris 10 printf not
handling printf (NULL).
Rainer
--
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Rainer Orth, Center for Biotechnology, Bielefeld University
