GRUB warning level increase

GRUB warning level increase

[Vladimir 'φ-coder/phcoder' Serbinenko]

Hello, all. I have increased the warning level in GRUB. This is done for 
quicker discovery and correction of the bugs which would be otherwise 
hard to track. Mostly it enabled warnings regarding guidelines which are 
already followed by GRUB.
Most important one is -Wcast-align. x86 doesn't enforce any alignment 
but the other platforms do. And since platform-independent code is 
usually written and tested on x86, it's important to ensure that it's 
properly aligned. The invariants checked by -Wcast-align give the 
necessary guarantee as long as void * isn't involved.
Some code  is difficult to write in a way to satisfy the warning and/or 
is platform-specific, in this case #pragma exceptions can be done.
For imported code we can add -Wno-* to module cflags for less important 
(mostly stylistic) warnings.
Also if some warnings are too annoying we can drop them.

-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko

Re: GRUB warning level increase

[Grégoire Sutre]

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On 02/10/2012 05:00 PM, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> Hello, all. I have increased the warning level in GRUB. This is done for
> quicker discovery and correction of the bugs which would be otherwise
> hard to track. Mostly it enabled warnings regarding guidelines which are
> already followed by GRUB.

On Debian GNU/Linux amd64 with GCC 4.6.2, I get a number of warnings
triggered by -Wunsafe-loop-optimizations. The first one is:

commands/lsacpi.c: In function 'grub_cmd_lsacpi':
commands/lsacpi.c:135:3: error: cannot optimize loop, the loop counter 
may overflow [-Werror=unsafe-loop-optimizations]
commands/lsacpi.c:166:3: error: cannot optimize loop, the loop counter 
may overflow [-Werror=unsafe-loop-optimizations]
cc1: all warnings being treated as errors

The attached patch fixes it.  The remaining ones are, afaics, either
false positives or potential overflows in loops of the form:

         for (i = 1; i <= foo; i++) { ... }

where i and foo have the same type (e.g., int).  I'm not sure how to
properly fix those (declare i with a wider type? replace i by i+1 in
the whole loop to make the condition become i < foo?).

Grégoire

[-- Attachment #2: check-len.diff --]
[-- Type: text/x-patch, Size: 854 bytes --]

=== modified file 'grub-core/commands/lsacpi.c'
--- grub-core/commands/lsacpi.c	2012-02-10 15:48:48 +0000
+++ grub-core/commands/lsacpi.c	2012-02-12 14:03:07 +0000
@@ -132,7 +132,7 @@ disp_acpi_xsdt_table (struct grub_acpi_t
   disp_acpi_table (t);
   len = t->length - sizeof (*t);
   desc = (grub_uint64_t *) (t + 1);
-  for (; len > 0; desc++, len -= sizeof (*desc))
+  for (; len >= sizeof (*desc); desc++, len -= sizeof (*desc))
     {
 #if GRUB_CPU_SIZEOF_VOID_P == 4
       if (*desc >= (1ULL << 32))
@@ -163,7 +163,7 @@ disp_acpi_rsdt_table (struct grub_acpi_t
   disp_acpi_table (t);
   len = t->length - sizeof (*t);
   desc = (grub_uint32_t *) (t + 1);
-  for (; len > 0; desc++, len -= sizeof (*desc))
+  for (; len >= sizeof (*desc); desc++, len -= sizeof (*desc))
     {
       t = (struct grub_acpi_table_header *) (grub_addr_t) *desc;