[PATCH v2] bitmap: Use g_try_new0/g_renew

[PATCH v2] bitmap: Use g_try_new0/g_renew

[Paolo Bonzini]

Avoids an explicit use of sizeof().  The GLib allocation macros
ensure that the multiplication by the size of the element
uses the right type and does not overflow.

While at it, change bitmap_new() to use g_new0 directly.  Its current
impl of calling bitmap_try_new() followed by a plain abort() has
worse diagnostics than g_new0, which uses g_error to report the actual
allocation size that failed.

Cc: qemu-trivial@nongnu.org
Cc: Roman Kiryanov <rkir@google.com>
Cc: Daniel Berrange <berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/qemu/bitmap.h | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/include/qemu/bitmap.h b/include/qemu/bitmap.h
index 97806811eeb..1cf288445f3 100644
--- a/include/qemu/bitmap.h
+++ b/include/qemu/bitmap.h
@@ -92,17 +92,14 @@ long slow_bitmap_count_one(const unsigned long *bitmap, long nbits);
 
 static inline unsigned long *bitmap_try_new(long nbits)
 {
-    long len = BITS_TO_LONGS(nbits) * sizeof(unsigned long);
-    return g_try_malloc0(len);
+    long nelem = BITS_TO_LONGS(nbits);
+    return g_try_new0(unsigned long, nelem);
 }
 
 static inline unsigned long *bitmap_new(long nbits)
 {
-    unsigned long *ptr = bitmap_try_new(nbits);
-    if (ptr == NULL) {
-        abort();
-    }
-    return ptr;
+    long nelem = BITS_TO_LONGS(nbits);
+    return g_new0(unsigned long, nelem);
 }
 
 static inline void bitmap_zero(unsigned long *dst, long nbits)
@@ -265,10 +262,10 @@ unsigned long bitmap_find_next_zero_area(unsigned long *map,
 static inline unsigned long *bitmap_zero_extend(unsigned long *old,
                                                 long old_nbits, long new_nbits)
 {
-    long new_len = BITS_TO_LONGS(new_nbits) * sizeof(unsigned long);
-    unsigned long *new = g_realloc(old, new_len);
-    bitmap_clear(new, old_nbits, new_nbits - old_nbits);
-    return new;
+    long new_nelem = BITS_TO_LONGS(new_nbits);
+    unsigned long *ptr = g_renew(unsigned long, old, new_nelem);
+    bitmap_clear(ptr, old_nbits, new_nbits - old_nbits);
+    return ptr;
 }
 
 void bitmap_to_le(unsigned long *dst, const unsigned long *src,
-- 
2.44.0

Re: [PATCH v2] bitmap: Use g_try_new0/g_renew

[Daniel P. Berrangé]

On Thu, May 02, 2024 at 05:22:42PM +0200, Paolo Bonzini wrote:
> Avoids an explicit use of sizeof().  The GLib allocation macros
> ensure that the multiplication by the size of the element
> uses the right type and does not overflow.
> 
> While at it, change bitmap_new() to use g_new0 directly.  Its current
> impl of calling bitmap_try_new() followed by a plain abort() has
> worse diagnostics than g_new0, which uses g_error to report the actual
> allocation size that failed.
> 
> Cc: qemu-trivial@nongnu.org
> Cc: Roman Kiryanov <rkir@google.com>
> Cc: Daniel Berrange <berrange@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  include/qemu/bitmap.h | 19 ++++++++-----------
>  1 file changed, 8 insertions(+), 11 deletions(-)

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


With regards,
Daniel
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