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memory: make it safer to expand arrays

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* src/util/memory.h (VIR_REALLOC_N): Update docs.
(VIR_EXPAND_N, VIR_SHRINK_N): New macros.
(virAlloc, virAllocN, virReallocN, virAllocVar, virFree): Add some
gcc attributes.
* src/util/memory.c (virExpandN, virShrinkN): New functions.
(virReallocN): Update docs.
* src/libvirt_private.syms: Export new helpers.
* docs/hacking.html.in: Prefer newer interfaces over
VIR_REALLOC_N, since uninitialized memory can bite us.
* HACKING: Regenerate.
This commit is contained in:
Eric Blake
2010-11-18 12:11:43 -07:00
parent b503022e57
commit 5a0beacc12
5 changed files with 148 additions and 41 deletions
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HACKING
+21 -17
View File
@@ -280,9 +280,9 @@ Low level memory management
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 memory.h
routines, use the macros from memory.h.
- e.g. to allocate a single object:
- To allocate a single object:
virDomainPtr domain;
@@ -293,10 +293,10 @@ routines, use the macros from memory.h
- e.g. to allocate an array of objects
- To allocate an array of objects:
virDomainPtr domains;
int ndomains = 10;
size_t ndomains = 10;
if (VIR_ALLOC_N(domains, ndomains) < 0) {
virReportOOMError();
@@ -305,7 +305,7 @@ routines, use the macros from memory.h
- e.g. to allocate an array of object pointers
- To allocate an array of object pointers:
virDomainPtr *domains;
int ndomains = 10;
@@ -317,18 +317,22 @@ routines, use the macros from memory.h
- e.g. to re-allocate the array of domains to be longer
- To re-allocate the array of domains to be longer:
ndomains = 20
if (VIR_REALLOC_N(domains, ndomains) < 0) {
if (VIR_EXPAND_N(domains, ndomains, 10) < 0) {
virReportOOMError();
return NULL;
}
- e.g. to free the domain
- To trim an array of domains to have one less element:
VIR_SHRINK_N(domains, ndomains, 1);
- To free the domain:
VIR_FREE(domain);
@@ -344,7 +348,7 @@ code base to help avoiding double-closing of files or file descriptors, which
is particulary dangerous in a multi-threaded applications. Instead of these
APIs, use the macros from files.h
- eg opening a file from a file descriptor
- Open a file from a file descriptor:
if ((file = VIR_FDOPEN(fd, "r")) == NULL) {
virReportSystemError(errno, "%s",
@@ -355,7 +359,7 @@ APIs, use the macros from files.h
- e.g. close a file descriptor
- Close a file descriptor:
if (VIR_CLOSE(fd) < 0) {
virReportSystemError(errno, "%s", _("failed to close file"));
@@ -363,7 +367,7 @@ APIs, use the macros from files.h
- eg close a file
- Close a file:
if (VIR_FCLOSE(file) < 0) {
virReportSystemError(errno, "%s", _("failed to close file"));
@@ -371,8 +375,8 @@ APIs, use the macros from files.h
- eg close a file or file descriptor in an error path, without losing the
previous "errno" value
- Close a file or file descriptor in an error path, without losing the previous
"errno" value:
VIR_FORCE_CLOSE(fd);
VIR_FORCE_FCLOSE(file);
@@ -460,7 +464,7 @@ If there is a need for complex string concatenations, avoid using the usual
sequence of malloc/strcpy/strcat/snprintf functions and make use of the
virBuffer API described in buf.h
eg typical usage is as follows:
Typical usage is as follows:
char *
somefunction(...)
@@ -594,7 +598,7 @@ When using goto, please use one of these standard labels if it makes sense:
error: A path only taken upon return with an error code
cleanup: A path taken upon return with success code + optional error
no_memory: A path only taken upon return with an OOM error code
retry: If needing to jump upwards (eg retry on EINTR)
retry: If needing to jump upwards (e.g., retry on EINTR)
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