[Openmp-commits] [openmp] [OpenMP] Improve dladdr error handling in ompd_init() (PR #201043)

[Mark Zhuang via Openmp-commits]

================
@@ -87,8 +87,10 @@ void ompd_init() {
   Dl_info dl_info;
   int ret = dladdr((void *)ompd_init, &dl_info);
   if (!ret) {
-    fprintf(stderr, "%s\n", dlerror());
-  } else if (strrchr(dl_info.dli_fname, '/')) {
+    const char *err = dlerror();
+    if (err)
+      fprintf(stderr, "dladdr failed in ompd_init: %s\n", err);
----------------
zqb-all wrote:

Thanks @jprotze and @mjklemm for the suggestions. 

To print the hint only when debugging, I see two options:

**Option A — move the `OMP_DEBUG` check before `dladdr` and gate the message on it:**
```c
const char *ompd_env_var = getenv("OMP_DEBUG");
int ompd_debug = ompd_env_var && !strcmp(ompd_env_var, "enabled");

#if KMP_OS_UNIX
  ...
  if (!ret) {
    const char *err = dlerror();
    if (ompd_debug || err)
      fprintf(stderr,
              "The OpenMP runtime could not determine the location of "
              "libompd.so. If the debugger fails to load the library, make "
              "sure to add the directory containing a compatible libompd.so "
              "to your LD_LIBRARY_PATH%s%s\n",
              err ? ": " : "", err ? err : "");
  } ...
#endif
```

**Option B — use libomp's trace facility (as @mjklemm suggested):**
```c
  if (!ret) {
    const char *err = dlerror();
    KA_TRACE(10, ("The OpenMP runtime could not determine the location of "
                  "libompd.so. If the debugger fails to load the library, make "
                  "sure to add the directory containing a compatible libompd.so "
                  "to your LD_LIBRARY_PATH%s%s\n",
                  err ? ": " : "", err ? err : ""));
  } 
```

Do you have a preference between the two? Happy to go either way.

https://github.com/llvm/llvm-project/pull/201043