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| Code Block | ||||
|---|---|---|---|---|
| ||||
#include <stddef.h>
size_t getlen(const int *input, size_t maxlen, int delim) {
for (size_t i = 0; i < maxlen; ++i) {
if (input[i] == delim) {
return i;
}
}
}
void func(int userdata) {
size_t i;
int data[] = { 1, 1, 1 };
i = getlen(data, sizeof(data), 0);
data[i] = userdata;
} |
Implementation Details
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(GCC)
Violating this rule can have unexpected consequences, as in the following example:
The following program violates this rule:
| Code Block | ||||
|---|---|---|---|---|
| ||||
#include <stdio.h>
size_t getlen(const int *input, size_t maxlen, int delim) {
for (size_t i = 0; i < maxlen; ++i) {
if (input[i] == delim) {
return i;
}
}
}
int main(int argc, char **argv) {
size_t i;
int data[] = { 1, 1, 1 };
i = getlen(data, sizeof(data), 0);
printf("Returned: %zu\n", i);
data[i] = 0;
return 0;
} |
...
| Code Block |
|---|
example.c: In function 'getlen': example.c:12: warning: control reaches end of non-void function |
When run None of the inputs to the function equal the delimiter, so when run with GCC 4.4.3 on Linux, control reaches the value of i is 5, as if end of the getlen() function returned which returns 5, causing an out-of-bounds write to the data array.
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