fatal error: invalid pointer found on stack about go_ibm_db HOT 6 CLOSED

Update / FYI:

We executed our application (which uses this module) with the -gcflags=all=-d=checkptr arguments, which reported two issues with unsafe pointers. One in initDriver in driver.go and one in Conn.setAutoCommitAttr in tx.go.

By applying the changes from asifjalil/cli@2598d7f into a local fork of this module, we got rid of the unsafe pointer warnings. Our application builds and runs fine with the modified go_ibm_db fork, but since the fatal error: invalid pointer found on stack error is very rare we'll need much more testing before we can say for sure it solved our problems.

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@eriklupander Could you please provide script/steps to reproduce this issue would be helpful. Thanks.

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Hi,

the actual error with fatal error: invalid pointer found on stack is very hard to reproduce, it happens so rarely I cannot really create a program that certainly would reproduce the problem.

However, you can easily check the go_ibm_db module's codebase for bad pointer usage by entering the /testdata folder and run:

go run -gcflags=all=-d=checkptr main.go

This results in (truncated) running locally on my Mac:

fatal error: checkptr: pointer arithmetic computed bad pointer value

goroutine 1 [running, locked to thread]:
runtime.throw({0x10012a140?, 0x1000cfe40?})
	/usr/local/opt/go/libexec/src/runtime/panic.go:1047 +0x5d fp=0xc000066c38 sp=0xc000066c08 pc=0x10003491d
runtime.checkptrArithmetic(0x1?, {0x0?, 0x1001f0000?, 0x10034a9a8?})
	/usr/local/opt/go/libexec/src/runtime/checkptr.go:52 +0xbb fp=0xc000066c68 sp=0xc000066c38 pc=0x10000919b
github.com/ibmdb/go_ibm_db.initDriver()
	/Users/<username>/golang/pkg/mod/github.com/ibmdb/[email protected]/driver.go:37 +0xb2 fp=0xc000066ce0 sp=0xc000066c68 pc=0x1000c6952
github.com/ibmdb/go_ibm_db.init.0()
	/Users/<username>/golang/pkg/mod/github.com/ibmdb/[email protected]/driver.go:62 +0x3f fp=0xc000066d20 sp=0xc000066ce0 pc=0x1000c6b9f
runtime.doInit(0x1001e78a0)

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@eriklupander
We are seeing the checkptr issue because this is a new feature added in Go 1.14
-d=checkptr as a compile-time option for adding instrumentation to check that Go code is following unsafe.Pointer safety rules dynamically. This can be disabled with -gcflags=all=-d=checkptr=0.
go run -gcflags=all=-d=checkptr=0 main.go

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Thanks for your answer.

The issue is that the code in driver.go and tx.go seems to be incorrect given that the checkptr check detects an issue. Turning off the checkptr check doesn't solve the root issue which is that we're getting those "invalid pointer found on stack" panics.

After applying the same fixes (in our local fork of this module) as in asifjalil/cli@2598d7f we have not seen any more panics and the checkptr check runs without complaining.

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Fix for this issue has been delivered using PR #215. Closing the issue now. Thanks.

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