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[RFC,v2,22/22] softmmu/physmem: Clean up local variable shadowing

Message ID 20230904161235.84651-23-philmd@linaro.org
State Superseded
Headers show
Series (few more) Steps towards enabling -Wshadow | expand

Commit Message

Philippe Mathieu-Daudé Sept. 4, 2023, 4:12 p.m. UTC
Fix:

  softmmu/physmem.c: In function ‘cpu_physical_memory_snapshot_and_clear_dirty’:
  softmmu/physmem.c:916:27: warning: declaration of ‘offset’ shadows a parameter [-Wshadow=compatible-local]
    916 |             unsigned long offset = page % DIRTY_MEMORY_BLOCK_SIZE;
        |                           ^~~~~~
  softmmu/physmem.c:892:31: note: shadowed declaration is here
    892 |     (MemoryRegion *mr, hwaddr offset, hwaddr length, unsigned client)
        |                        ~~~~~~~^~~~~~

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
RFC: Please double-check how 'offset' is used few lines later.
---
 softmmu/physmem.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Comments

Daniel P. Berrangé Sept. 4, 2023, 4:31 p.m. UTC | #1
On Mon, Sep 04, 2023 at 06:12:34PM +0200, Philippe Mathieu-Daudé wrote:
> Fix:
> 
>   softmmu/physmem.c: In function ‘cpu_physical_memory_snapshot_and_clear_dirty’:
>   softmmu/physmem.c:916:27: warning: declaration of ‘offset’ shadows a parameter [-Wshadow=compatible-local]
>     916 |             unsigned long offset = page % DIRTY_MEMORY_BLOCK_SIZE;
>         |                           ^~~~~~
>   softmmu/physmem.c:892:31: note: shadowed declaration is here
>     892 |     (MemoryRegion *mr, hwaddr offset, hwaddr length, unsigned client)
>         |                        ~~~~~~~^~~~~~
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
> RFC: Please double-check how 'offset' is used few lines later.

I don't see an issue - those lines are in an outer scope, so won't
be accessing the 'offset' you've changed, they'll be the parameter
instead. If you want to sanity check though, presumably the asm
dissassembly for this method should be the same before/after this
change

> ---
>  softmmu/physmem.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

> 
> diff --git a/softmmu/physmem.c b/softmmu/physmem.c
> index 18277ddd67..db5b628a60 100644
> --- a/softmmu/physmem.c
> +++ b/softmmu/physmem.c
> @@ -913,16 +913,16 @@ DirtyBitmapSnapshot *cpu_physical_memory_snapshot_and_clear_dirty
>  
>          while (page < end) {
>              unsigned long idx = page / DIRTY_MEMORY_BLOCK_SIZE;
> -            unsigned long offset = page % DIRTY_MEMORY_BLOCK_SIZE;
> +            unsigned long ofs = page % DIRTY_MEMORY_BLOCK_SIZE;
>              unsigned long num = MIN(end - page,
> -                                    DIRTY_MEMORY_BLOCK_SIZE - offset);
> +                                    DIRTY_MEMORY_BLOCK_SIZE - ofs);
>  
> -            assert(QEMU_IS_ALIGNED(offset, (1 << BITS_PER_LEVEL)));
> +            assert(QEMU_IS_ALIGNED(ofs, (1 << BITS_PER_LEVEL)));
>              assert(QEMU_IS_ALIGNED(num,    (1 << BITS_PER_LEVEL)));
> -            offset >>= BITS_PER_LEVEL;
> +            ofs >>= BITS_PER_LEVEL;
>  
>              bitmap_copy_and_clear_atomic(snap->dirty + dest,
> -                                         blocks->blocks[idx] + offset,
> +                                         blocks->blocks[idx] + ofs,
>                                           num);
>              page += num;
>              dest += num >> BITS_PER_LEVEL;
> -- 
> 2.41.0
> 
> 

With regards,
Daniel
Peter Xu Sept. 5, 2023, 3:50 p.m. UTC | #2
On Mon, Sep 04, 2023 at 05:31:30PM +0100, Daniel P. Berrangé wrote:
> On Mon, Sep 04, 2023 at 06:12:34PM +0200, Philippe Mathieu-Daudé wrote:
> > Fix:
> > 
> >   softmmu/physmem.c: In function ‘cpu_physical_memory_snapshot_and_clear_dirty’:
> >   softmmu/physmem.c:916:27: warning: declaration of ‘offset’ shadows a parameter [-Wshadow=compatible-local]
> >     916 |             unsigned long offset = page % DIRTY_MEMORY_BLOCK_SIZE;
> >         |                           ^~~~~~
> >   softmmu/physmem.c:892:31: note: shadowed declaration is here
> >     892 |     (MemoryRegion *mr, hwaddr offset, hwaddr length, unsigned client)
> >         |                        ~~~~~~~^~~~~~
> > 
> > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> > ---
> > RFC: Please double-check how 'offset' is used few lines later.
> 
> I don't see an issue - those lines are in an outer scope, so won't
> be accessing the 'offset' you've changed, they'll be the parameter
> instead. If you want to sanity check though, presumably the asm
> dissassembly for this method should be the same before/after this
> change

(and if it didn't do so then it's a bug..)

> 
> > ---
> >  softmmu/physmem.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

Reviewed-by: Peter Xu <peterx@redhat.com>
diff mbox series

Patch

diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 18277ddd67..db5b628a60 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -913,16 +913,16 @@  DirtyBitmapSnapshot *cpu_physical_memory_snapshot_and_clear_dirty
 
         while (page < end) {
             unsigned long idx = page / DIRTY_MEMORY_BLOCK_SIZE;
-            unsigned long offset = page % DIRTY_MEMORY_BLOCK_SIZE;
+            unsigned long ofs = page % DIRTY_MEMORY_BLOCK_SIZE;
             unsigned long num = MIN(end - page,
-                                    DIRTY_MEMORY_BLOCK_SIZE - offset);
+                                    DIRTY_MEMORY_BLOCK_SIZE - ofs);
 
-            assert(QEMU_IS_ALIGNED(offset, (1 << BITS_PER_LEVEL)));
+            assert(QEMU_IS_ALIGNED(ofs, (1 << BITS_PER_LEVEL)));
             assert(QEMU_IS_ALIGNED(num,    (1 << BITS_PER_LEVEL)));
-            offset >>= BITS_PER_LEVEL;
+            ofs >>= BITS_PER_LEVEL;
 
             bitmap_copy_and_clear_atomic(snap->dirty + dest,
-                                         blocks->blocks[idx] + offset,
+                                         blocks->blocks[idx] + ofs,
                                          num);
             page += num;
             dest += num >> BITS_PER_LEVEL;