<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/88356>88356</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            False Positive - null dereference in clang-tidy
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang-tidy
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          mushenoy
      </td>
    </tr>
</table>

<pre>
    A False positive in clang-tidy for below sample program.

**sample.c**

```
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>

double (*cosine)(double) = NULL;
extern void test (void);

int
main(int argc, char **argv)
{
    void *handle;

    handle = dlopen("libtest.so", RTLD_LAZY);
    if (!handle) {
        exit(EXIT_FAILURE);
    }

   cosine = dlsym(handle, "cos");
   if (cosine) {
       test();
       printf("%f\n", cosine (2.0));
    }
    dlclose(handle);
    exit(EXIT_SUCCESS);
}
```

**Warnings**:
```
clang-tidy --checks="clang-analyzer-*" /tmp/sample.c
Error while trying to load a compilation database:
Could not auto-detect compilation database for file "/tmp/sample.c"
No compilation database found in /tmp or any parent directory
fixed-compilation-database: Error while opening fixed database: No such file or directory
json-compilation-database: Error while opening JSON database: No such file or directory
Running without flags.
1 warning generated.
/tmp/sample.c:21:23: warning: Called function pointer is null (null dereference) [clang-analyzer-core.CallAndMessage]
   21 |        printf("%f\n", cosine (2.0));
      |                       ^~~~~~
/tmp/sample.c:14:9: note: Assuming 'handle' is non-null
   14 |     if (!handle) {
      |         ^~~~~~~
/tmp/sample.c:14:5: note: Taking false branch
   14 |     if (!handle) {
      |     ^
/tmp/sample.c:19:8: note: Assuming 'cosine' is non-null
   19 |    if (cosine) {
      |        ^~~~~~
/tmp/sample.c:19:4: note: Taking true branch
   19 |    if (cosine) {
      |    ^
/tmp/sample.c:20:8: note: Null pointer value stored to 'cosine'
   20 |        test();
      |        ^~~~~~
/tmp/sample.c:21:23: note: Called function pointer is null (null dereference)
   21 |        printf("%f\n", cosine (2.0));
      |                       ^~~~~~
 ```
 **Version**
clang-tidy  --version
LLVM (http://llvm.org/):
  LLVM version 19.0.0
 
 **Observations:**
 
- Warnings are not reported if the cosine function ptr is made as a local variable
- Warnings are not reported if the test function definition is provided
- Warnings are not reported if the test() function call is removed
- Warnings are not reported if the “= NULL” is removed in line 5.
- Warnings are still reported even if the function ptr is made as static variable



</pre>
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