Re: [PATCH] [aarch64, testsuite] Document the ARM_CC_FOR_TARGET testsuite variable

[Luis Machado <luis.machado@arm.com>]

On 6/9/22 15:30, Pedro Alves wrote:
> 
> On 2022-06-09 14:06, Luis Machado wrote:
>> This variable is useful when exercising AArch64 multi-arch support (debugging
>> 32-bit AArch32 executables).
>>
>> Unfortunately it isn't well documented. This patch adds information about it
>> and explains how to use it.
>> ---
>>   gdb/testsuite/README | 28 ++++++++++++++++++++++++++++
>>   1 file changed, 28 insertions(+)
>>
>> diff --git a/gdb/testsuite/README b/gdb/testsuite/README
>> index 3a34dcdd154..5b3fde75ece 100644
>> --- a/gdb/testsuite/README
>> +++ b/gdb/testsuite/README
>> @@ -736,3 +736,31 @@ Use [is_remote target] to check whether the DejaGnu target board is
>>   remote.  When what you really want to know is whether GDB is using the
>>   remote protocol, because feature X is only available when GDB debugs
>>   natively, check gdb_protocol instead.
>> +
>> +Architecture-specific settings
>> +******************************
> 
> The non-architecture-specific settings are actually called "parameters", as in:
> 
>   Testsuite Parameters
>   ********************
> 
> I think your new section should come right after that one, and be called
> 
> "Architecture-specific Parameters"
> 
>> +
>> +This section documents architecture-specific settings and flags that can be
> 
> s/settings and flags/parameters/
> 
>> +used with the GDB testsuite.
>> +
>> +- AArch64 (Linux)
>> +
> 
> There should be a line with the parameter name before describing it, like in
> the generic section.  Just:
> 
> ARM_CC_FOR_TARGET
> 
> followed by an empty line.
> 
>> +The AArch64 ports of GDB and GDBserver support debugging AArch32 32-bit
>> +programs running on 64-bit state.  There are some tests under gdb.multi/
>> +that exercise this particular feature.
>> +
> 
> ...
> 
>> +The tests will attempt to find a compiler capable of generating 32-bit
> 
> "attempt to find" here sound a bit odd here, since with the variable set, the
> testsuite doesn't try to find anything, it assumes what we specify works.
> See below.
> 
>> +executables through the ARM_CC_FOR_TARGET variable.  This variable should
>> +contain the command line for the compiler, including the full path to it, if
>> +the compiler is not in $PATH.
>> +
>> +If ARM_CC_FOR_TARGET is not set, the testsuite will guess some compiler
>> +commands.  If none is found, or if the 32-bit executable generated by
>> +compiler can't be executed correctly, the tests will be marked UNSUPPORTED.
>> +
>> +The list of 32-bit Arm compiler names the testsuite will try can be found
>> +in gdb/testsuite/lib/gdb.exp:arm_cc_for_target.
>> +
> 
> I suggest swapping around the description to first say what happens by
> default, and then talk about overriding the default.  Like this:
> 
> ARM_CC_FOR_TARGET
> 
> The AArch64 ports of GDB and GDBserver support debugging AArch32
> 32-bit programs running on 64-bit state.  There are some tests under
> gdb.multi/ that exercise this particular feature.
> 
> By default, the testsuite tries to find a compiler capable of
> generating 32-bit executables.  If no compiler is found, or if the
> 32-bit executable generated by the found compiler can't be executed
> correctly, the tests will be marked UNSUPPORTED.  The list of 32-bit
> Arm compiler names the testsuite will try can be found in
> gdb/testsuite/lib/gdb.exp:arm_cc_for_target.
> 
> You can set ARM_CC_FOR_TARGET to override the search and explicitly
> specify the compiler to use.  This variable should contain the command
> line for the compiler, including the full path to it, if the compiler
> is not in $PATH.
> 
>> +Example invocation:
>> +
>> +make check-gdb TESTS="gdb.multi/multi-arch.exp" RUNTESTFLAGS="ARM_CC_FOR_TARGET=arm-linux-gnueabihf-gcc"
> 
> The command line should be indended, like all the other example invocations in the file.
> 
> Otherwise LGTM.

Thanks. I've made those changes locally and pushed it as 3abc1d8fe0e09a4ba806d5e2a1902ac45f825ee9.