Re: [PATCH-for-8.0] block/dmg: Ignore C99 prototype declaration mismatch from <lzfse.h>

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

+Marc-André & Paolo

On 27/3/23 19:08, Stefan Weil wrote:
> Am 27.03.23 um 17:13 schrieb Philippe Mathieu-Daudé:
> 
>> When liblzfe (Apple LZFSE compression library) is present
>> (for example installed via 'brew') on Darwin, QEMU build
>> fails as:
>>
>>    Has header "lzfse.h" : YES
>>    Library lzfse found: YES
>>
>>      Dependencies
>>        lzo support                  : NO
>>        snappy support               : NO
>>        bzip2 support                : YES
>>        lzfse support                : YES
>>        zstd support                 : YES 1.5.2
>>
>>      User defined options
>>        dmg                          : enabled
>>        lzfse                        : enabled
>>
>>    [221/903] Compiling C object libblock.fa.p/block_dmg-lzfse.c.o
>>    FAILED: libblock.fa.p/block_dmg-lzfse.c.o
>>    /opt/homebrew/Cellar/lzfse/1.0/include/lzfse.h:56:43: error: this 
>> function declaration is not a prototype [-Werror,-Wstrict-prototypes]
>>    LZFSE_API size_t lzfse_encode_scratch_size();
>>                                              ^
>>                                               void
>>    /opt/homebrew/Cellar/lzfse/1.0/include/lzfse.h:94:43: error: this 
>> function declaration is not a prototype [-Werror,-Wstrict-prototypes]
>>    LZFSE_API size_t lzfse_decode_scratch_size();
>>                                              ^
>>                                               void
>>    2 errors generated.
>>    ninja: build stopped: subcommand failed.
>>
>> This issue has been reported in the lzfse project in 2016:
>> https://github.com/lzfse/lzfse/issues/3#issuecomment-226574719
>>
>> Since the project seems unmaintained, simply ignore the
>> strict-prototypes warning check for the <lzfse.h> header,
>> similarly to how we deal with the GtkItemFactoryCallback
>> prototype from <gtk/gtkitemfactory.h>, indirectly included
>> by <gtk/gtk.h>.
>>
>> Cc: Julio Faracco <jcfaracco@gmail.com>
>> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
>> ---
>>   block/dmg-lzfse.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/block/dmg-lzfse.c b/block/dmg-lzfse.c
>> index 6798cf4fbf..0abc970bf6 100644
>> --- a/block/dmg-lzfse.c
>> +++ b/block/dmg-lzfse.c
>> @@ -23,7 +23,12 @@
>>    */
>>   #include "qemu/osdep.h"
>>   #include "dmg.h"
>> +
>> +/* Work around an -Wstrict-prototypes warning in LZFSE headers */
> 
> 
> "Work around a -Wstrict-prototypes" ("a" instead of "an")?
> 
> 
>> +#pragma GCC diagnostic push
>> +#pragma GCC diagnostic ignored "-Wstrict-prototypes"
>>   #include <lzfse.h>
>> +#pragma GCC diagnostic pop
>>   static int dmg_uncompress_lzfse_do(char *next_in, unsigned int 
>> avail_in,
>>                                      char *next_out, unsigned int 
>> avail_out)
> 
> 
> The warning can also be suppressed if the build uses `-isystem 
> /opt/homebrew/include` instead of `-I/opt/homebrew/include` as I just 
> have tested.

IIUC by design meson only allows including *relative* directories,
and manage the system ones:
https://mesonbuild.com/Include-directories.html

> If we can find a solution how to implement that I thing it would look 
> nicer. Technically the patch looks good.
> 
> Reviewed-by: Stefan Weil <sw@weilnetz.de>

Thanks!