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glx: createcontext: silence analyzer warning and make code easier to understand 

This warning is probably a false alarm, but it's trivial to fix.

| ../glx/createcontext.c: In function ‘__glXDisp_CreateContextAttribsARB’:
| ../glx/createcontext.c:172:24: warning: dereference of NULL ‘0’ [CWE-476] [-Wanalyzer-null-dereference]
|   172 |         switch (attribs[i * 2]) {
|       |                 ~~~~~~~^~~~~~~

The situation is too complex for the analyzer to handle:
(but also not immediately clear for the human reader)

* `attribs` is only NULL when req->numAttribs is 0
* in that case, the for loop is no-op, so `attribs` won't ever be deref'ed.

We can make it easier for both analyzer as well as human reader by just putting
the whole loop into an `if (req->numAttribs)` and assigning it inside there.
There shouldn't be any (practically measurable) extra cost.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
This commit is contained in:
Enrico Weigelt, metux IT consult 2025-05-06 14:31:42 +02:00
parent 2b3bbce30b
commit 9ee96639d7
1 changed files with 51 additions and 49 deletions
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10
glx/createcontext.c
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@ -80,8 +80,6 @@ __glXDisp_CreateContextAttribsARB(__GLXclientState * cl, GLbyte * pc)
{
ClientPtr client = cl->client;
xGLXCreateContextAttribsARBReq *req = (xGLXCreateContextAttribsARBReq *) pc;
int32_t *attribs = (req->numAttribs != 0) ? (int32_t *) (req + 1) : NULL;
unsigned i;
int major_version = 1;
int minor_version = 0;
uint32_t flags = 0;
@ -168,7 +166,11 @@ __glXDisp_CreateContextAttribsARB(__GLXclientState * cl, GLbyte * pc)
}
}
for (i = 0; i < req->numAttribs; i++) {
int32_t *attribs = NULL;
if (req->numAttribs) {
attribs = (int32_t *) (req + 1);
for (int i = 0; i < req->numAttribs; i++) {
switch (attribs[i * 2]) {
case GLX_CONTEXT_MAJOR_VERSION_ARB:
major_version = attribs[2 * i + 1];
@ -198,7 +200,6 @@ __glXDisp_CreateContextAttribsARB(__GLXclientState * cl, GLbyte * pc)
if (reset != GLX_NO_RESET_NOTIFICATION_ARB
&& reset != GLX_LOSE_CONTEXT_ON_RESET_ARB)
return BadValue;
break;
case GLX_CONTEXT_RELEASE_BEHAVIOR_ARB:
@ -227,6 +228,7 @@ __glXDisp_CreateContextAttribsARB(__GLXclientState * cl, GLbyte * pc)
break;
}
}
}
/* The GLX_ARB_create_context spec says:
*