Re: debugging libgo failures

[Ian Lance Taylor <iant@golang.org>]

On Tue, Mar 12, 2019 at 11:20 AM Aldy Hernandez <aldyh@redhat.com> wrote:
>
> I have some libgo failures which I'm pretty sure I caused (see below for
> details), but I can't seem to figure out how to reproduce.  Before I go
> down the rabbit hole, is there an easy way of reproducing say:
>
> FAIL: database/sql
> FAIL: net/http
>
> I'm used to scouring
> x86_64-pc-linux-gnu/libWHATEVER/testsuite/libWHATEVER.log and gaining
> insight on how to manually run tests.  However, there's nothing in
> libgo/testsuite, and libgo/libgo.log just has a summary of tests.
>
> Ideally I'd like a way of building a test (with say -fdump-tree-all),
> and/or sticking gdb on the resulting executable.

To run a test, cd to the libgo build directly (TARGET/libgo) and run
`make database/sql/check`.  To see the exact commands that it runs,
including how the compiler is invoked, run `make GOTESTFLAGS=--trace
database/sql/check`.  To leave the directory behind with the test
program, run `make GOTESTFLAGS=--keep database/sql/check`.  That will
leave a gotestNNNN/test directory.  In that directory you can run
`LD_LIBRARY_PATH=../../.libs ./a.out -test.short` to run the tests.
You can run specific failing tests using a -test.run option.  You can
of course run gdb on the program.

Hope that helps.

Ian


> --- FAIL: TestMaxIdleConns (0.00s)
>      sql_test.go:1789: freeConns after set to zero = -1; want 0
>      sql_test.go:1798: freeConns = -1; want 0
> panic: runtime error: makeslice: cap out of range [recovered]
>          panic: runtime error: makeslice: cap out of range
>
> goroutine 202 [running]:
> panic
>          /home/cygnus/aldyh/src/gcc/libgo/go/runtime/panic.go:588
> testing.tRunner..func1
>          /home/cygnus/aldyh/src/gcc/libgo/go/testing/testing.go:765
> panic
>          /home/cygnus/aldyh/src/gcc/libgo/go/runtime/panic.go:535
> database..z2fsql.DB.Close
>
> /home/cygnus/aldyh/bld/ranger/x86_64-pc-linux-gnu/libgo/gotest51314/test/sql.go:768
> sql.closeDB
>
> /home/cygnus/aldyh/bld/ranger/x86_64-pc-linux-gnu/libgo/gotest51314/test/sql_test.go:140
> database..z2fsql.TestMaxIdleConns
>
> /home/cygnus/aldyh/bld/ranger/x86_64-pc-linux-gnu/libgo/gotest51314/test/sql_test.go:1800
> testing.tRunner
>          /home/cygnus/aldyh/src/gcc/libgo/go/testing/testing.go:827
> created by testing.T.Run
>          /home/cygnus/aldyh/src/gcc/libgo/go/testing/testing.go:878 +1163
> FAIL: database/sql
>
>
> [snip]
> [snip]
>
> net..z2fhttp.persistConn.writeLoop
>
> /home/cygnus/aldyh/bld/ranger/x86_64-pc-linux-gnu/32/libgo/gotest2965/test/transport.go:1888
> created by net..z2fhttp.Transport.dialConn
>
> /home/cygnus/aldyh/bld/ranger/x86_64-pc-linux-gnu/32/libgo/gotest2965/test/transport.go:1339
> +2693
>
> eax    0x0
> ebx    0x2
> ecx    0xcbbdd84c
> edx    0x0
> edi    0x0
> esi    0x8
> ebp    0xcbbdd84c
> esp    0xcbbdd830
> eip    0xf7f93049
> eflags 0x286
> cs     0x23
> fs     0x0
> gs     0x63
> FAIL: net/http