[RFA] Avoid expect's buffer overflow in info-var.exp test.

[Andrew Burgess]

* Philippe Waroquiers <philippe.waroquiers@skynet.be> [2019-08-31 17:36:56 +0200]:

> Once the executable is started, info variables can show thousands
> of variables belonging to glibc (see below).
> 
> This long list of variables then causes the test to fail, due
> to expect's buffer overflow:
>   Running /bd/home/philippe/gdb/git/build_binutils-gdb/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.base/info-var.exp ...
>   ERROR: internal buffer is full.
>   ERROR: internal buffer is full.
>   ERROR: internal buffer is full.
> 
> Fix this by running testing 'info variables' without running the
> executable.
> 
> gdb ./info-var
> ...
> Reading symbols from ./info-var...
> (gdb) |info variables|wc
>      27      54     971
> (gdb) start
> Temporary breakpoint 1 at 0x1129: file /bd/home/philippe/gdb/git/build_binutils-gdb/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.base/info-var-f1.c, line 23.
> Starting program: /bd/home/philippe/gdb/git/build_binutils-gdb/gdb/testsuite/outputs/gdb.base/info-var/info-var
> 
> Temporary breakpoint 1, main ()
>     at /bd/home/philippe/gdb/git/build_binutils-gdb/gdb/testsuite/../../../binutils-gdb/gdb/testsuite/gdb.base/info-var-f1.c:23
> 23	  return global_var + get_offset() + f1_var;
> (gdb) |info variables|wc
>    4334   14581  130738
> (gdb)
> 
> gdb/testsuite/ChangeLog
> YYYY-MM-DD  Philippe Waroquiers  <philippe.waroquiers@skynet.be>
> 
> 	* gdb.base/info-var.exp: Test info variables without running
> 	to main, to avoid expect's buffer overflow.

Seems reasonable to me.

Thanks,
Andrew

> ---
>  gdb/testsuite/gdb.base/info-var.exp | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/gdb/testsuite/gdb.base/info-var.exp b/gdb/testsuite/gdb.base/info-var.exp
> index 6dd896d8aa..c9b7485ffb 100644
> --- a/gdb/testsuite/gdb.base/info-var.exp
> +++ b/gdb/testsuite/gdb.base/info-var.exp
> @@ -22,10 +22,9 @@ if {[prepare_for_testing "failed to prepare" \
>      return -1
>  }
>  
> -if ![runto_main] then {
> -    fail "can't run to main"
> -    return 0
> -}
> +# Note: we do not run to main, as otherwise, the output of info variables
> +# can be very long, showing thousands of glibc variables.
> +# This long output then causes expect's buffer to overflow.
>  
>  gdb_test "info variables" \
>      [multi_line \
> -- 
> 2.20.1
>