One AST failure, one false positive when testing our codebase.

[Sebastian Andersson]

I tried cppcheck 2.6.2 (and c7ef602cd6d58af2ef3d5a7ec01b53dded03cc05) on our C codebase and got these two problems. Perhaps someone with access to be bug tracker can add them there?

#include <stdint.h>

int func(void)
{
    static uint32_t v;

    if (++v == 0) {
        ++v;
        return 1;
    }
    return 0;
}

It gives the following output:

 test.c:7:13: style: Condition '++v==0' is always false [knownConditionTrueFalse]
    if (++v == 0) {
            ^

This is perhaps a variant of #10248 ?

A function converting one enum to another in a creative way fails with a broken AST error:

typedef enum {
    A,
    B,
    C
} enum1_t;

typedef enum {
    D,
    E,
    F
} enum2_t;

enum2_t func1(enum1_t v)
{
    return (enum2_t[]) {
        [A] = D,
        [B] = E,
        [C] = F
    }[v];
}

enum2_t func2(enum1_t v)
{
    enum2_t ret;
    ret = (enum2_t[]) {
        [A] = D,
        [B] = E,
        [C] = F
    }[v];
    return ret;
}

func1 works fine, func2 fails with:

test2.c:25:9: error: Syntax Error: AST broken, binary operator '=' doesn't have two operands. [internalAstError]
    ret = (enum2_t[]) {
        ^

[CHR]

In the first case, you are relying on unsigned overflow, right?
The second example should be covered by https://trac.cppcheck.net/ticket/10177

[Sebastian Andersson]

Yes, its with unsigned overflow.

I missed 10177 when I searched for it, sorry about that.

[CHR]

No worries. Here is a ticket for the first issue: https://trac.cppcheck.net/ticket/10616