fix: catch exceptions in print-uncaught-messages destructor (#5103)

Fixes #5063

In that issue, it was reported that the printing of any unretrieved
error messages upon destruction of an ImageBuf could itself have an
exception (including if it, for some reason, could not correctly fwrite
the output). And if that is the case, it could terminate the app.

So for safety, this patch encloses this particular print statement in a
try/catch. And also found another in ErrorHolder in the internals of
Strutil, which is used for "global" errors issued to OIIO::errorfmt().

Assisted-by: Claude Code / Opus 4.6

I did the fix in ImageBuf, then Claude found the other spot in
ErrorHolder that also needed the fix.

Signed-off-by: Larry Gritz <lg@larrygritz.com>

Author: lgritz

src/libOpenImageIO/imagebuf.cpp

@@ -575,10 +575,15 @@ ImageBufImpl::~ImageBufImpl()
     // how to properly check for errors.
     if (!m_err.empty() /* Note: safe becausethis is the dtr */
         && OIIO::pvt::imagebuf_print_uncaught_errors) {
-        OIIO::print(
-            "An ImageBuf was destroyed with a pending error message that was never\n"
-            "retrieved via ImageBuf::geterror(). This was the error message:\n{}\n",
-            m_err);
+        try {
+            OIIO::print(
+                "An ImageBuf was destroyed with a pending error message that was never\n"
+                "retrieved via ImageBuf::geterror(). This was the error message:\n{}\n",
+                m_err);
+        } catch (...) {
+            // Swallow any exceptions (e.g., from fmt's fwrite_fully)
+            // to avoid std::terminate from throwing in a destructor.
+        }
     }
 }
 

src/libutil/strutil.cpp

@@ -201,10 +201,15 @@ struct ErrorHolder {
     ~ErrorHolder()
     {
         if (!error_msg.empty() && OIIO::pvt::oiio_print_uncaught_errors) {
-            OIIO::print(
-                "OpenImageIO exited with a pending error message that was never\n"
-                "retrieved via OIIO::geterror(). This was the error message:\n{}\n",
-                error_msg);
+            try {
+                OIIO::print(
+                    "OpenImageIO exited with a pending error message that was never\n"
+                    "retrieved via OIIO::geterror(). This was the error message:\n{}\n",
+                    error_msg);
+            } catch (...) {
+                // Swallow any exceptions (e.g., from fmt's fwrite_fully)
+                // to avoid std::terminate from throwing in a destructor.
+            }
         }
     }
 };