Re: [PATCH v2 1/2] configure: Fix building with SASL on Windows

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 3/9/20 1:30 PM, Daniel P. Berrangé wrote:
> On Mon, Mar 09, 2020 at 01:24:53PM +0100, Philippe Mathieu-Daudé wrote:
>> The Simple Authentication and Security Layer (SASL) library
>> re-defines the struct iovec on Win32 [*]. QEMU also re-defines
>> it in "qemu/osdep.h". The two definitions then clash on a MinGW
>> build.
>> We can avoid the SASL definition by defining STRUCT_IOVEC_DEFINED.
>> Since QEMU already defines 'struct iovec' if it is missing, add
>> the definition to vnc_sasl_cflags to avoid SASL re-defining it.
>>
>> [*] https://github.com/cyrusimap/cyrus-sasl/blob/cyrus-sasl-2.1.27/include/sasl.h#L187
>>
>> Cc: Alexey Pavlov <alexpux@gmail.com>
>> Cc: Biswapriyo Nath <nathbappai@gmail.com>
>> Reported-by: Youry Metlitsky <winaes@yandex.ru>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
>> ---
>> v2:
>> Since QEMU provides 'struct iovec' if missing, always define
>> STRUCT_IOVEC_DEFINED (danpb review).
>> ---
>>   configure | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/configure b/configure
>> index cbf864bff1..a4cd4bccfb 100755
>> --- a/configure
>> +++ b/configure
>> @@ -3349,7 +3349,9 @@ if test "$vnc" = "yes" && test "$vnc_sasl" != "no" ; then
>>   int main(void) { sasl_server_init(NULL, "qemu"); return 0; }
>>   EOF
>>     # Assuming Cyrus-SASL installed in /usr prefix
>> -  vnc_sasl_cflags=""
>> +  # QEMU defines struct iovec in "qemu/osdep.h",
>> +  # we don't want libsasl to redefine it in <sasl/sasl.h>.
>> +  vnc_sasl_cflags="-DSTRUCT_IOVEC_DEFINED"
>>     vnc_sasl_libs="-lsasl2"
>>     if compile_prog "$vnc_sasl_cflags" "$vnc_sasl_libs" ; then
>>       vnc_sasl=yes
> 
> This works so:
> 
>    Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> 
> 
> however, I'm wondering if we'd be better doing this in a more
> localized place. This applies to everything we compile, but
> only one place imports sasl.h, so should we instead do
> 
>     #define STRUCT_IOVEC_DEFINED
>     #include <sasl/saslh.>
> 
> in vnc-auth-sasl.h, so we localize the namespace pollution.

Good idea, but we'll need to remember this fix if we ever use 
<sasl/sasl.h> in another header.

> 
> Regards,
> Daniel
>