Re: [PATCH edk2-platforms v2 06/18] ARM/VExpressPkg: Add and update debug ASSERTS

[Evan Lloyd <Evan.Lloyd@arm.com>]

Hi Leif, Ard.
Can I get you two argue out the pros and cons of the "ASSERT(FALSE)" debate, please.
(see https://lists.01.org/pipermail/edk2-devel/2018-January/019788.html)
For what it is worth, our (surprisingly unanimous) opinion is that, since the ASSERT is only there to help spot a problem, then the more information reported the better.  The only benefits of ASSERT(FALSE) would be a smaller debug image and minor efficiency improvement on the path to the crash.

Regards,
Evan

> -----Original Message-----
> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> Sent: 04 January 2018 19:55
> To: Evan Lloyd <Evan.Lloyd@arm.com>
> Cc: Girish Pathak <Girish.Pathak@arm.com>; Matteo Carlini
> <Matteo.Carlini@arm.com>; nd <nd@arm.com>; edk2-devel@lists.01.org;
> Thomas Abraham <thomas.abraham@arm.com>; Arvind Chauhan
> <Arvind.Chauhan@arm.com>; leif.lindholm@linaro.org
> Subject: Re: [edk2] [PATCH edk2-platforms v2 06/18] ARM/VExpressPkg:
> Add and update debug ASSERTS
> 
> On 4 January 2018 at 19:51, Evan Lloyd <Evan.Lloyd@arm.com> wrote:
> >
> >
> >> -----Original Message-----
> >> From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> >> Sent: 04 January 2018 19:24
> >> To: Girish Pathak <Girish.Pathak@arm.com>
> >> Cc: Evan Lloyd <Evan.Lloyd@arm.com>; Matteo Carlini
> >> <Matteo.Carlini@arm.com>; nd <nd@arm.com>; edk2-
> devel@lists.01.org;
> >> Thomas Abraham <thomas.abraham@arm.com>; Arvind Chauhan
> >> <Arvind.Chauhan@arm.com>; leif.lindholm@linaro.org
> >> Subject: Re: [edk2] [PATCH edk2-platforms v2 06/18] ARM/VExpressPkg:
> >> Add and update debug ASSERTS
> >>
> >> On 4 January 2018 at 18:55, Girish Pathak <Girish.Pathak@arm.com>
> >> wrote:
> >> > Hi Ard,
> >> >
> >> >> -----Original Message-----
> >> >> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On
> >> >> Behalf Of Ard Biesheuvel
> >> >> Sent: 23 December 2017 14:12
> >> >> To: Evan Lloyd <Evan.Lloyd@arm.com>
> >> >> Cc: "Matteo.Carlini@arm.com"@arm.com;
> >> >> "leif.lindholm@linaro.org"@arm.com; "nd@arm.com"@arm.com;
> edk2-
> >> >> devel@lists.01.org; Thomas Abraham <thomas.abraham@arm.com>;
> >> Arvind
> >> >> Chauhan <Arvind.Chauhan@arm.com>;
> >> "ard.biesheuvel@linaro.org"@arm.com
> >> >> Subject: Re: [edk2] [PATCH edk2-platforms v2 06/18]
> ARM/VExpressPkg:
> >> >> Add and update debug ASSERTS
> >> >>
> >> >> On 22 December 2017 at 19:08,  <evan.lloyd@arm.com> wrote:
> >> >> > From: Girish Pathak <girish.pathak at arm.com>
> >> >> >
> >> >> > This change adds some debug assertions e.g to catch NULL pointer
> >> >> > errors missing in PL11Lcd and HdLcd platform libraries.
> >> >> >
> >> >> > Contributed-under: TianoCore Contribution Agreement 1.1
> >> >> > Signed-off-by: Girish Pathak <girish.pathak@arm.com>
> >> >> > Signed-off-by: Evan Lloyd <evan.lloyd@arm.com>
> >> >> > ---
> >> >> >
> >> >>
> >>
> Platform/ARM/VExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVExp
> >> r
> >> >> ess.c       | 22 +++++++++++++++++-
> >> >> >
> >> >> >
> >> >>
> >>
> Platform/ARM/VExpressPkg/Library/PL111LcdArmVExpressLib/PL111LcdAr
> >> m
> >> >> VEx
> >> >> > press.c | 24 +++++++++++++++++++-
> >> >> >  2 files changed, 44 insertions(+), 2 deletions(-)
> >> >> >
> >> >> > diff --git
> >> >> >
> >> >>
> >>
> a/Platform/ARM/VExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVE
> >> x
> >> >> pres
> >> >> > s.c
> >> >> >
> >> >>
> >>
> b/Platform/ARM/VExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVE
> >> x
> >> >> pres
> >> >> > s.c index
> >> >> >
> >> >>
> >>
> 6afd764897f49c64490ce891682f99bb0f5d993b..a8fe8696da0653017ce9fa
> >> 6e4a
> >> >> 86
> >> >> > caf283bc04c9 100644
> >> >> > ---
> >> >> >
> >> >>
> >>
> a/Platform/ARM/VExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVE
> >> x
> >> >> pres
> >> >> > s.c
> >> >> > +++
> >> >>
> >>
> b/Platform/ARM/VExpressPkg/Library/HdLcdArmVExpressLib/HdLcdArmVE
> >> x
> >> >> > +++ press.c
> >> >> > @@ -153,6 +153,9 @@ LcdPlatformGetVram (
> >> >> >    EFI_STATUS              Status;
> >> >> >    EFI_ALLOCATE_TYPE       AllocationType;
> >> >> >
> >> >> > +  ASSERT (VramBaseAddress != NULL);  ASSERT (VramSize != NULL);
> >> >> > +
> >> >> >    // Set the vram size
> >> >> >    *VramSize = LCD_VRAM_SIZE;
> >> >> >
> >> >> > @@ -171,6 +174,7 @@ LcdPlatformGetVram (
> >> >> >                    VramBaseAddress
> >> >> >                    );
> >> >> >    if (EFI_ERROR (Status)) {
> >> >> > +    ASSERT (FALSE);
> >> >> >      return Status;
> >> >> >    }
> >> >> >
> >> >> > @@ -181,8 +185,8 @@ LcdPlatformGetVram (
> >> >> >                    *VramSize,
> >> >> >                    EFI_MEMORY_WC
> >> >> >                    );
> >> >> > -  ASSERT_EFI_ERROR (Status);
> >> >> >    if (EFI_ERROR (Status)) {
> >> >> > +    ASSERT (FALSE);
> >> >>
> >> >> As in the sibling patch against EDK2, this patch makes it more
> >> >> difficult to figure out what went wrong when you hit the ASSERT.
> >> >> ASSERT_EFI_ERROR prints the value of Status, ASSERT(FALSE) only
> >> >> prints
> >> >> '0 != 1'
> >> >>
> >> >
> >> > This change(and other similar changes) is in response to review
> >> > comments on patch v1
> >> > https://lists.01.org/pipermail/edk2-devel/2017-October/015995.html
> >> >
> >> > with above reference, Can you please confirm if we should revert to
> >> > the
> >> patch v1 version ?
> >> >
> >>
> >> I guess Leif and I are in disagreement here. In particular, I think
> >> his comment
> >>
> >> """
> >> ASSERT (FALSE)?  (You already know Status is an EFI_ERROR, and a
> >> console message saying ASSERT (Status) is not getting you out of
> >> looking at the source code to find out what happened.) """
> >>
> >> is misguided, given that ASSERT_EFI_ERROR (Status) will actually
> >> print the value of Status to the debug console.
> >>
> >> However, the objections against putting function calls in ASSERT()s
> >> are
> >> justified: ASSERT() should not have side effects if its condition is
> >> met, and function calls may have side effects.
> >>
> >> I suppose we should wait for Leif to return on the 22nd before
> >> proceeding with the review.
> >> Apologies for the confusion, and for the delay.
> >
> >  [[Evan Lloyd]] An alternative might be for Girish to take the other route
> Leif suggested, and cache the condition in a variable.
> > That might be a slight overhead, and the (presumably BOOLEAN) variable
> may need careful naming, but...
> >
> 
> If we are going to use a boolean to record the result of the comparison, and
> ASSERT() on it in the if () block if the comparison is false, I don't see what
> the difference is with doing ASSERT (FALSE) directly.
> 
> 
> >>
> >>
> >>
> >> >> >      gBS->FreePages (*VramBaseAddress, EFI_SIZE_TO_PAGES
> >> (*VramSize));
> >> >> >      return Status;
> >> >> >    }
> >> >> > @@ -221,6 +225,7 @@ LcdPlatformSetMode (
> >> >> >    EFI_STATUS            Status;
> >> >> >
> >> >> >    if (ModeNumber >= LcdPlatformGetMaxMode ()) {
> >> >> > +    ASSERT (FALSE);
> >> >>
> >> >> These are fine: the code itself explains adequately which
> >> >> condition triggered the ASSERT to fire.
> >> >>
> >> >> >      return EFI_INVALID_PARAMETER;
> >> >> >    }
> >> >> >
> >> >> > @@ -279,7 +284,10 @@ LcdPlatformQueryMode (
> >> >> >    OUT EFI_GRAPHICS_OUTPUT_MODE_INFORMATION * CONST
> Info
> >> >> >    )
> >> >> >  {
> >> >> > +  ASSERT (Info != NULL);
> >> >> > +
> >> >> >    if (ModeNumber >= LcdPlatformGetMaxMode ()) {
> >> >> > +    ASSERT (FALSE);
> >> >> >      return EFI_INVALID_PARAMETER;
> >> >> >    }
> >> >> >
> >> >> > @@ -343,7 +351,18 @@ LcdPlatformGetTimings (
> >> >> >    OUT UINT32 * CONST                            VFrontPorch
> >> >> >    )
> >> >> >  {
> >> >> > +  // One of the pointers is NULL  ASSERT (HRes != NULL);
> >> >> > + ASSERT (HSync != NULL);  ASSERT (HBackPorch != NULL);  ASSERT
> >> >> > + (HFrontPorch != NULL);  ASSERT (VRes != NULL);  ASSERT (VSync
> >> >> > + != NULL);  ASSERT (VBackPorch != NULL);  ASSERT (VFrontPorch
> >> >> > + != NULL);
> >> >> > +
> >> >> >    if (ModeNumber >= LcdPlatformGetMaxMode ()) {
> >> >> > +    ASSERT (FALSE);
> >> >> >      return EFI_INVALID_PARAMETER;
> >> >> >    }
> >> >> >
> >> >> > @@ -376,6 +395,7 @@ LcdPlatformGetBpp (
> >> >> >    )
> >> >> >  {
> >> >> >    if (ModeNumber >= LcdPlatformGetMaxMode ()) {
> >> >> > +    ASSERT (FALSE);
> >> >> >      return EFI_INVALID_PARAMETER;
> >> >> >    }
> >> >> >
> >> >> > diff --git
> >> >> >
> >> >>
> >>
> a/Platform/ARM/VExpressPkg/Library/PL111LcdArmVExpressLib/PL111Lcd
> >> Ar
> >> >> mV
> >> >> > Express.c
> >> >> >
> >> >>
> >>
> b/Platform/ARM/VExpressPkg/Library/PL111LcdArmVExpressLib/PL111Lcd
> >> Ar
> >> >> mV
> >> >> > Express.c index
> >> >> >
> >> >>
> >>
> 799fb3fc781ce04bb64cb1fa0b87f262a670ed78..fd4eea8f8e2397bc7d4ddf
> >> 4cfe
> >> >> 3d
> >> >> > cc97a5109edb 100644
> >> >> > ---
> >> >> >
> >> >>
> >>
> a/Platform/ARM/VExpressPkg/Library/PL111LcdArmVExpressLib/PL111Lcd
> >> Ar
> >> >> mV
> >> >> > Express.c
> >> >> > +++
> >> >>
> >>
> b/Platform/ARM/VExpressPkg/Library/PL111LcdArmVExpressLib/PL111Lcd
> >> >> > +++ ArmVExpress.c
> >> >> > @@ -205,6 +205,9 @@ LcdPlatformGetVram (
> >> >> >
> >> >> >    Status = EFI_SUCCESS;
> >> >> >
> >> >> > +  ASSERT (VramBaseAddress != NULL);  ASSERT (VramSize != NULL);
> >> >> > +
> >> >> >    // Is it on the motherboard or on the daughterboard?
> >> >> >    switch (PL111_CLCD_SITE) {
> >> >> >
> >> >> > @@ -225,6 +228,7 @@ LcdPlatformGetVram (
> >> >> >                      VramBaseAddress
> >> >> >                      );
> >> >> >      if (EFI_ERROR (Status)) {
> >> >> > +      ASSERT (FALSE);
> >> >> >        return Status;
> >> >> >      }
> >> >> >
> >> >> > @@ -235,8 +239,8 @@ LcdPlatformGetVram (
> >> >> >                      *VramSize,
> >> >> >                      EFI_MEMORY_WC
> >> >> >                      );
> >> >> > -    ASSERT_EFI_ERROR (Status);
> >> >> >      if (EFI_ERROR (Status)) {
> >> >> > +      ASSERT (FALSE);
> >> >> >        gBS->FreePages (*VramBaseAddress, EFI_SIZE_TO_PAGES
> >> >> (*VramSize));
> >> >> >        return Status;
> >> >> >      }
> >> >> > @@ -294,6 +298,7 @@ LcdPlatformSetMode (
> >> >> >    UINT32                SysId;
> >> >> >
> >> >> >    if (ModeNumber >= LcdPlatformGetMaxMode ()) {
> >> >> > +    ASSERT (FALSE);
> >> >> >      return EFI_INVALID_PARAMETER;
> >> >> >    }
> >> >> >
> >> >> > @@ -369,7 +374,10 @@ LcdPlatformQueryMode (
> >> >> >    OUT EFI_GRAPHICS_OUTPUT_MODE_INFORMATION * CONST Info
> >> >> >    )
> >> >> >  {
> >> >> > +  ASSERT (Info != NULL);
> >> >> > +
> >> >> >    if (ModeNumber >= LcdPlatformGetMaxMode ()) {
> >> >> > +    ASSERT (FALSE);
> >> >> >      return EFI_INVALID_PARAMETER;
> >> >> >    }
> >> >> >
> >> >> > @@ -433,7 +441,18 @@ LcdPlatformGetTimings (
> >> >> >    OUT UINT32 * CONST                      VFrontPorch
> >> >> >    )
> >> >> >  {
> >> >> > +  // One of the pointers is NULL  ASSERT (HRes != NULL);
> >> >> > + ASSERT (HSync != NULL);  ASSERT (HBackPorch != NULL);  ASSERT
> >> >> > + (HFrontPorch != NULL);  ASSERT (VRes != NULL);  ASSERT (VSync
> >> >> > + != NULL);  ASSERT (VBackPorch != NULL);  ASSERT (VFrontPorch
> >> >> > + != NULL);
> >> >> > +
> >> >> >    if (ModeNumber >= LcdPlatformGetMaxMode ()) {
> >> >> > +    ASSERT (FALSE);
> >> >> >      return EFI_INVALID_PARAMETER;
> >> >> >    }
> >> >> >
> >> >> > @@ -465,7 +484,10 @@ LcdPlatformGetBpp (
> >> >> >    OUT LCD_BPP * CONST                     Bpp
> >> >> >    )
> >> >> >  {
> >> >> > +  ASSERT (Bpp != NULL);
> >> >> > +
> >> >> >    if (ModeNumber >= LcdPlatformGetMaxMode ()) {
> >> >> > +    ASSERT (FALSE);
> >> >> >      return EFI_INVALID_PARAMETER;
> >> >> >    }
> >> >> >
> >> >> > --
> >> >> > Guid("CE165669-3EF3-493F-B85D-6190EE5B9759")
> >> >> >
> >> >> > _______________________________________________
> >> >> > edk2-devel mailing list
> >> >> > edk2-devel@lists.01.org
> >> >> > https://lists.01.org/mailman/listinfo/edk2-devel
> >> >> _______________________________________________
> >> >> edk2-devel mailing list
> >> >> edk2-devel@lists.01.org
> >> >> https://lists.01.org/mailman/listinfo/edk2-devel