Re: [PATCH] gdb/testsuite: Bump up 'match_max'

[Thiago Jung Bauermann <thiago.bauermann@linaro.org>]

Hello Simon,

Thanks for looking into this.

Simon Marchi <simark@simark.ca> writes:

> On 2023-10-03 15:53, Thiago Jung Bauermann via Gdb-patches wrote:
>> This fixes "ERROR: internal buffer is full." in gdb.base/maint.exp when
>> running with "make check-read1".
>> 
>> Also take the opportunity to fix stray whitespace in the vicinity.
>> ---
>>  gdb/testsuite/lib/gdb.exp | 9 +++++----
>>  1 file changed, 5 insertions(+), 4 deletions(-)
>> 
>> diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
>> index de22da8d8a8c..c6ee4628f8f5 100644
>> --- a/gdb/testsuite/lib/gdb.exp
>> +++ b/gdb/testsuite/lib/gdb.exp
>> @@ -6533,13 +6533,14 @@ proc default_gdb_init { test_file_name } {
>>      if { $gdb_wrapper_target != [current_target_name] } {
>>  	set gdb_wrapper_initialized 0
>>      }
>> -    
>> +
>>      # Unlike most tests, we have a small number of tests that generate
>>      # a very large amount of output.  We therefore increase the expect
>>      # buffer size to be able to contain the entire test output.  This
>> -    # is especially needed by gdb.base/info-macros.exp.
>> -    match_max -d 65536
>> -    # Also set this value for the currently running GDB. 
>> +    # is especially needed by gdb.base/info-macros.exp and
>> +    # gdb.base/maint.exp.
>> +    match_max -d 196608
>> +    # Also set this value for the currently running GDB.
>>      match_max [match_max -d]
>>  
>>      # We want to add the name of the TCL testcase to the PASS/FAIL messages.
>
> Do you have details about what fails specifically?  It runs fine here,

I think that what causes trouble is the fact that the line tables of the
dynamic linker are huge.

What happens is that when testing "maint info line-table w/o a file
name", expect times out in the middle of "maint info line-table" output
while it's listing the line-table of dl-load.c. A bit after that I get
the first 2 "ERROR: internal buffer is full." (I get between 2 and 5
such ERRORs depending on the machine).

Then there are a few more errors while printing the line table of
elf/rtld.c.

> so I'm curious which part of the test fills the buffer exactly.  Also,

Interesting. This fails on all 4 of the machines I tried, covering
aarch64-linux, armv8l-linux-gnueabihf and x86_84-linux. Do you have
libc6 debuginfo installed?

In any case, I put the testsuite logs of regular "make check" and "make
check-read1" with default timeout and with 3600s timeout for
gdb.base/maint.exp here:

https://people.linaro.org/~thiago.bauermann/read1-maint.exp/

> my understanding is that check-read1 should have no effect on this, it
> shouldn't fill the buffer more than a regular "make check".  It only
> makes it such that read system calls return at most 1 byte.

I don't know how expect manages its internal buffer. I initially wrote
that "maybe timed out tests cause the unmatched output accumulate in the
buffer?", but then I tested with gdb_test_timeout set to 3600: I didn't
get timeouts anymore, but I still got the "internal buffer is full"
errors, which caused the respective tests to be marked UNRESOLVED.

So all this to say that I don't know what is going on, TBH...

-- 
Thiago