[libvirt] [PATCH v3 03/19] util: use glib memory allocation functions
Daniel P. Berrangé
berrange at redhat.com
Thu Oct 10 10:53:57 UTC 2019
Convert the VIR_ALLOC family of APIs with use of the g_malloc family of
APIs. Use of VIR_ALLOC related functions should be incrementally phased
out over time, allowing return value checks to be dropped. Use of
VIR_FREE should be replaced with auto-cleanup whenever possible.
We previously used the 'calloc-posix' gnulib module because mingw does
not set errno to ENOMEM on failure.
Reviewed-by: Ján Tomko <jtomko at redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
---
bootstrap.conf | 1 -
docs/hacking.html.in | 106 +++++--------------------------------------
src/util/viralloc.c | 29 +++---------
src/util/viralloc.h | 9 ++++
4 files changed, 27 insertions(+), 118 deletions(-)
diff --git a/bootstrap.conf b/bootstrap.conf
index 358d783a6b..7d73584809 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -26,7 +26,6 @@ byteswap
c-ctype
c-strcase
c-strcasestr
-calloc-posix
canonicalize-lgpl
chown
clock-time
diff --git a/docs/hacking.html.in b/docs/hacking.html.in
index 2e064ced5e..8072796312 100644
--- a/docs/hacking.html.in
+++ b/docs/hacking.html.in
@@ -1008,102 +1008,20 @@ BAD:
</p>
<dl>
+ <dt>VIR_ALLOC, VIR_REALLOC, VIR_RESIZE_N, VIR_EXPAND_N,
+ VIR_SHRINK_N, VIR_FREE, VIR_APPEND_ELEMENT, VIR_INSERT_ELEMENT,
+ VIR_DELETE_ELEMENT</dt>
+ <dd>Prefer the GLib APIs g_new0/g_renew/g_free in most cases.
+ There should rarely be a need to use g_malloc/g_realloc.
+ Instead of using plain C arrays, it is preferrable to use
+ one of the GLib types, GArray, GPtrArray or GByteArray. These
+ all use a struct to track the array memory and size together
+ and efficiently resize. <strong>NEVER MIX</strong> use of the
+ classic libvirt memory allocation APIs and GLib APIs within
+ a single method. Keep the style consistent, converting existing
+ code to GLib style in a separate, prior commit.</dd>
</dl>
- <h2><a id="memalloc">Low level memory management</a></h2>
-
- <p>
- Use of the malloc/free/realloc/calloc APIs is deprecated in the libvirt
- codebase, because they encourage a number of serious coding bugs and do
- not enable compile time verification of checks for NULL. Instead of these
- routines, use the macros from viralloc.h.
- </p>
-
- <ul>
- <li><p>To allocate a single object:</p>
-
-<pre>
- virDomainPtr domain;
-
- if (VIR_ALLOC(domain) < 0)
- return NULL;
-</pre>
- </li>
-
- <li><p>To allocate an array of objects:</p>
-<pre>
- virDomainPtr domains;
- size_t ndomains = 10;
-
- if (VIR_ALLOC_N(domains, ndomains) < 0)
- return NULL;
-</pre>
- </li>
-
- <li><p>To allocate an array of object pointers:</p>
-<pre>
- virDomainPtr *domains;
- size_t ndomains = 10;
-
- if (VIR_ALLOC_N(domains, ndomains) < 0)
- return NULL;
-</pre>
- </li>
-
- <li><p>To re-allocate the array of domains to be 1 element
- longer (however, note that repeatedly expanding an array by 1
- scales quadratically, so this is recommended only for smaller
- arrays):</p>
-<pre>
- virDomainPtr domains;
- size_t ndomains = 0;
-
- if (VIR_EXPAND_N(domains, ndomains, 1) < 0)
- return NULL;
- domains[ndomains - 1] = domain;
-</pre></li>
-
- <li><p>To ensure an array has room to hold at least one more
- element (this approach scales better, but requires tracking
- allocation separately from usage)</p>
-
-<pre>
- virDomainPtr domains;
- size_t ndomains = 0;
- size_t ndomains_max = 0;
-
- if (VIR_RESIZE_N(domains, ndomains_max, ndomains, 1) < 0)
- return NULL;
- domains[ndomains++] = domain;
-</pre>
- </li>
-
- <li><p>To trim an array of domains from its allocated size down
- to the actual used size:</p>
-
-<pre>
- virDomainPtr domains;
- size_t ndomains = x;
- size_t ndomains_max = y;
-
- VIR_SHRINK_N(domains, ndomains_max, ndomains_max - ndomains);
-</pre></li>
-
- <li><p>To free an array of domains:</p>
-<pre>
- virDomainPtr domains;
- size_t ndomains = x;
- size_t ndomains_max = y;
- size_t i;
-
- for (i = 0; i < ndomains; i++)
- VIR_FREE(domains[i]);
- VIR_FREE(domains);
- ndomains_max = ndomains = 0;
-</pre>
- </li>
- </ul>
-
<h2><a id="file_handling">File handling</a></h2>
<p>
diff --git a/src/util/viralloc.c b/src/util/viralloc.c
index 10a8d0fb73..b8ca850764 100644
--- a/src/util/viralloc.c
+++ b/src/util/viralloc.c
@@ -45,10 +45,7 @@ VIR_LOG_INIT("util.alloc");
int virAlloc(void *ptrptr,
size_t size)
{
- *(void **)ptrptr = calloc(1, size);
- if (*(void **)ptrptr == NULL)
- abort();
-
+ *(void **)ptrptr = g_malloc0(size);
return 0;
}
@@ -69,10 +66,7 @@ int virAllocN(void *ptrptr,
size_t size,
size_t count)
{
- *(void**)ptrptr = calloc(count, size);
- if (*(void**)ptrptr == NULL)
- abort();
-
+ *(void**)ptrptr = g_malloc0_n(count, size);
return 0;
}
@@ -94,16 +88,7 @@ int virReallocN(void *ptrptr,
size_t size,
size_t count)
{
- void *tmp;
-
- if (xalloc_oversized(count, size))
- abort();
-
- tmp = realloc(*(void**)ptrptr, size * count);
- if (!tmp && ((size * count) != 0))
- abort();
-
- *(void**)ptrptr = tmp;
+ *(void **)ptrptr = g_realloc_n(*(void**)ptrptr, size, count);
return 0;
}
@@ -343,9 +328,7 @@ int virAllocVar(void *ptrptr,
abort();
alloc_size = struct_size + (element_size * count);
- *(void **)ptrptr = calloc(1, alloc_size);
- if (*(void **)ptrptr == NULL)
- abort();
+ *(void **)ptrptr = g_malloc0(alloc_size);
return 0;
}
@@ -362,7 +345,7 @@ void virFree(void *ptrptr)
{
int save_errno = errno;
- free(*(void**)ptrptr);
+ g_free(*(void**)ptrptr);
*(void**)ptrptr = NULL;
errno = save_errno;
}
@@ -395,7 +378,7 @@ void virDispose(void *ptrptr,
if (*(void**)ptrptr && count > 0)
memset(*(void **)ptrptr, 0, count * element_size);
- free(*(void**)ptrptr);
+ g_free(*(void**)ptrptr);
*(void**)ptrptr = NULL;
if (countptr)
diff --git a/src/util/viralloc.h b/src/util/viralloc.h
index 3e72e40bc9..517f9aada6 100644
--- a/src/util/viralloc.h
+++ b/src/util/viralloc.h
@@ -24,6 +24,15 @@
#include "internal.h"
+/**
+ * DEPRECATION WARNING
+ *
+ * APIs in this file should only be used when modifying existing code.
+ * Consider converting existing code to use the new APIs when touching
+ * it. All new code must use the GLib memory allocation APIs and/or
+ * GLib array data types. See the hacking file for more guidance.
+ */
+
/* Return 1 if an array of N objects, each of size S, cannot exist due
to size arithmetic overflow. S must be positive and N must be
nonnegative. This is a macro, not an inline function, so that it
--
2.21.0
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