posix.cfg: Improved configuration for swab().

cfg/posix.cfg

@@ -5496,6 +5496,7 @@ The function 'mktemp' is considered to be dangerous due to race conditions and s
     <leak-ignore/>
     <not-overlapping-data ptr1-arg="1" ptr2-arg="2" size-arg="3"/>
     <arg nr="1" direction="in">
+      <not-null/>
       <not-uninit/>
       <minsize type="argvalue" arg="3"/>
     </arg>

test/cfg/posix.c

@@ -431,6 +431,30 @@ void overlappingWriteFunction_swab(char *src, char *dest, ssize_t n)
     swab(src, src+3, 4);
 }
 
+void bufferAccessOutOfBounds_swab(char *src, char *dest, ssize_t n)
+{
+    // No warning shall be shown:
+    swab(dest, src, n);
+    char srcBuf[42] = {0};
+    char destBuf[42] = {0};
+    swab(srcBuf, dest, 42);
+    // cppcheck-suppress bufferAccessOutOfBounds
+    swab(srcBuf, dest, 43);
+    swab(src, destBuf, 42);
+    // cppcheck-suppress bufferAccessOutOfBounds
+    swab(src, destBuf, 43);
+}
+
+void nullPointer_swab(char *src, char *dest, ssize_t n)
+{
+    // No warning shall be shown:
+    swab(dest, src, n);
+    // cppcheck-suppress nullPointer
+    swab(NULL, dest, n);
+    // cppcheck-suppress nullPointer
+    swab(src, NULL, n);
+}
+
 bool invalidFunctionArgBool_isascii(bool b, int c)
 {
     // cppcheck-suppress invalidFunctionArgBool