| Issue |
109402
|
| Summary |
False positive "for loop analysis" warning
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
rHermes
|
This is tested with clang 18.1.0 on godbolt and occurs on trunk.
Here is the godbolt: https://godbolt.org/z/o3jhnoPso
Here is the code:
```c++
#include <iostream>
#include <vector>
/**
* Definition for singly-linked list.
*/
struct ListNode
{
int val;
ListNode* next;
ListNode() : val(0), next(nullptr) {}
ListNode(int x) : val(x), next(nullptr) {}
ListNode(int x, ListNode* next) : val(x), next(next) {}
};
class Solution
{
public:
static std::vector<std::vector<int>> spiralMatrix(const int M, const int N, ListNode const* head)
{
std::vector<std::vector<int>> out(M, std::vector<int>(N, -1));
const auto writeVal = [&](const int y, const int x) {
if (head) {
out[y][x] = head->val;
head = head->next;
}
};
// ok, we will loop in numbers.
for (int iter = 0; head; iter++) {
const int W = N - 2 * iter;
const int H = M - 2 * iter;
for (int j = 0; j < W; j++) {
writeVal(iter, iter + j);
}
for (int j = 1; j < H; j++) {
writeVal(iter + j, iter + W - 1);
}
for (int j = W - 2; 0 <= j; j--) {
writeVal(iter + H - 1, iter + j);
}
for (int j = H - 2; 0 < j; j--) {
writeVal(iter + j, iter);
}
}
return out;
}
};
```
If you compile this like so you get the following warning:
```c++
clang++ -Wall -Wextra -std=c++2a -Werror -o test test.cpp
<source>:31:24: error: variable 'head' used in loop condition not modified in loop body [-Werror,-Wfor-loop-analysis]
31 | for (int iter = 0; head; iter++) {
| ^~~~
```
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