Re: [PATCH] drm/i915: fix compilation warnings on maybe uninitialized pointers

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 29/11/2016 08:56, Daniel Vetter wrote:
> On Mon, Nov 28, 2016 at 06:43:19PM -0500, Jérémy Lefaure wrote:
>> Two warnings are produced by gcc (tested with gcc 6.2.1):
>>
>> drivers/gpu/drm/i915/intel_csr.c: In function ‘csr_load_work_fn’:
>> drivers/gpu/drm/i915/intel_csr.c:400:5: error: ‘fw’ is used
>> uninitialized in this function [-Werror=uninitialized]
>>   if (fw)
>>        ^
>> and
>>
>> In file included from drivers/gpu/drm/i915/i915_drv.h:47:0,
>>                  from drivers/gpu/drm/i915/intel_guc_loader.c:30:
>> drivers/gpu/drm/i915/intel_guc_loader.c: In function ‘intel_guc_init’:
>> ./include/drm/drmP.h:228:2: error: ‘fw’ may be used uninitialized in this
>> function  -Werror=maybe-uninitialized]
>>   drm_printk(KERN_DEBUG, DRM_UT_DRIVER, fmt, ##__VA_ARGS__)
>>   ^~~~~~~~~~
>> drivers/gpu/drm/i915/intel_guc_loader.c:595:25: note: ‘fw’ was declared here
>>   const struct firmware *fw;
>>                          ^~
>>
>> When CONFIG_DRM_I915_WERROR is set, those warnings break the build.
>>
>> Initializing fw pointer to NULL in both cases removes the warnings.
>>
>> Signed-off-by: Jérémy Lefaure <jeremy.lefaure@lse.epita.fr>
>
> Queued for -next, thanks for the patch.

I just wanted to reply with two things; first who can figure out why 
this hasn't been picked up by the compiler before? Or why GCC 6.2.1 on 
my machine does not complain? Looks like a real mystery!

And secondly the csr loader is not even checking the return code. I was 
about to suggest a v2 but never mind now. Can do it myself.

Regards,

Tvrtko

> -Daniel
>
>> ---
>>  drivers/gpu/drm/i915/intel_csr.c        | 2 +-
>>  drivers/gpu/drm/i915/intel_guc_loader.c | 2 +-
>>  2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
>> index d7a04bc..3520b3c 100644
>> --- a/drivers/gpu/drm/i915/intel_csr.c
>> +++ b/drivers/gpu/drm/i915/intel_csr.c
>> @@ -389,7 +389,7 @@ static void csr_load_work_fn(struct work_struct *work)
>>  {
>>  	struct drm_i915_private *dev_priv;
>>  	struct intel_csr *csr;
>> -	const struct firmware *fw;
>> +	const struct firmware *fw = NULL;
>>  	int ret;
>>
>>  	dev_priv = container_of(work, typeof(*dev_priv), csr.work);
>> diff --git a/drivers/gpu/drm/i915/intel_guc_loader.c b/drivers/gpu/drm/i915/intel_guc_loader.c
>> index 34d6ad2..ecfee49 100644
>> --- a/drivers/gpu/drm/i915/intel_guc_loader.c
>> +++ b/drivers/gpu/drm/i915/intel_guc_loader.c
>> @@ -592,7 +592,7 @@ static void guc_fw_fetch(struct drm_device *dev, struct intel_guc_fw *guc_fw)
>>  {
>>  	struct pci_dev *pdev = dev->pdev;
>>  	struct drm_i915_gem_object *obj;
>> -	const struct firmware *fw;
>> +	const struct firmware *fw = NULL;
>>  	struct guc_css_header *css;
>>  	size_t size;
>>  	int err;
>> --
>> 2.10.2
>>
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>
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