FP: for loop ignores condition

[Jochen Karrer]

In the for loop cppcheck-1.90 ignores the abort condition or the pre-initialization of a variable and generates a false positive warning:

#include <stdlib.h>

typedef struct ListEntry {
    struct ListEntry *next;
} ListEntry;

static ListEntry *listHead = NULL;

static void
InsertListEntry(ListEntry * newEntry)
 {   
    ListEntry *cursor, *prev;
    for (prev = NULL, cursor = listHead; cursor != NULL; prev = cursor, cursor = cursor->next) {
        /* Compare something and break */
    }   
    if (prev) {
        /* insert to middle of list */ 
    } else {
        /* This is a new list head */ 
    }   
}

Checking listEntry.c ...
listEntry.c:13:82: warning: Either the condition 'if(prev)' is redundant or there is possible null pointer dereference: cursor. [nullPointerRedundantCheck]
for (prev = NULL, cursor = listHead; cursor != NULL; prev = cursor, cursor = cursor->next) {
^
listEntry.c:16:8: note: Assuming that condition 'if(prev)' is not redundant
if (prev) {
^
listEntry.c:13:65: note: Assignment from 'cursor'
for (prev = NULL, cursor = listHead; cursor != NULL; prev = cursor, cursor = cursor->next) {
^
listEntry.c:13:82: note: Null pointer dereference
for (prev = NULL, cursor = listHead; cursor != NULL; prev = cursor, cursor = cursor->next) {

[Daniel Marjamäki]

Thanks! I can reproduce with cppcheck HEAD. It's somehow related to our data flow analysis. I created this ticket: https://trac.cppcheck.net/ticket/9701