feat(ImageBuf): auto print uncaught IB errors

src/include/OpenImageIO/imageio.h

@@ -2905,7 +2905,7 @@ OIIO_API std::string geterror(bool clear = true);
 ///    you should raise this limit. Setting the limit to 0 means having no
 ///    limit.
 ///
-/// - `int log_times`
+/// - `int log_times` (0)
 ///
 ///    When the `"log_times"` attribute is nonzero, `ImageBufAlgo` functions
 ///    are instrumented to record the number of times they were called and
@@ -2923,6 +2923,20 @@ OIIO_API std::string geterror(bool clear = true);
 ///    the log information. When the `log_times` attribute is disabled,
 ///    there is no additional performance cost.
 ///
+/// - `imagebuf:print_uncaught_errors` (1)
+///
+///   If nonzero, an `ImageBuf` upon destruction will print any error messages
+///   that were never retrieved by its `geterror()` method. While this may
+///   seem chaotic, we are presuming that any well-written library or
+///   application will proactively check error codes and retrieve errors, so
+///   will never print anything upon destruction. But for less sophisticated
+///   applications (or users), this is very useful for forcing display of
+///   error messages so that users can see relevant errors even if they never
+///   check them explicitly, thus self-diagnose their troubles before asking
+///   the project dev deam for help. Advanced users who for some reason desire
+///   to neither retrieve errors themselves nor have them printed in this
+///   manner can disable the behavior by setting this attribute to 0.
+///
 OIIO_API bool attribute(string_view name, TypeDesc type, const void* val);
 
 /// Shortcut attribute() for setting a single integer.

src/libOpenImageIO/imagebuf.cpp

@@ -485,6 +485,16 @@ ImageBufImpl::~ImageBufImpl()
     // else init_spec requested the system-wide shared cache, which
     // does not need to be destroyed.
     clear();
+
+    // Upon destruction, print uncaught errors to help users who don't know
+    // how to properly check for errors.
+    if (!m_err.empty() /* Note: safe becausethis is the dtr */
+        && 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);
+    }
 }
 
 

src/libOpenImageIO/imagebuf_test.cpp

@@ -501,6 +501,16 @@ test_write_over()
 
 
 
+static void
+test_uncaught_error()
+{
+    ImageBuf buf;
+    buf.error("Boo!");
+    // buf exists scope and is destroyed without anybody retrieving the error.
+}
+
+
+
 int
 main(int /*argc*/, char* /*argv*/[])
 {
@@ -534,6 +544,8 @@ main(int /*argc*/, char* /*argv*/[])
 
     test_write_over();
 
+    test_uncaught_error();
+
     Filesystem::remove("A_imagebuf_test.tif");
     return unit_test_failures;
 }

src/libOpenImageIO/imageio.cpp

@@ -52,6 +52,7 @@ int dds_bc5normal(0);
 int limit_channels(1024);
 int limit_imagesize_MB(std::min(32 * 1024,
                                 int(Sysutil::physical_memory() >> 20)));
+int imagebuf_print_uncaught_errors(1);
 ustring font_searchpath(Sysutil::getenv("OPENIMAGEIO_FONTS"));
 ustring plugin_searchpath(OIIO_DEFAULT_PLUGIN_SEARCHPATH);
 std::string format_list;         // comma-separated list of all formats
@@ -344,6 +345,10 @@ attribute(string_view name, TypeDesc type, const void* val)
         limit_imagesize_MB = *(const int*)val;
         return true;
     }
+    if (name == "imagebuf:print_uncaught_errors" && type == TypeInt) {
+        imagebuf_print_uncaught_errors = *(const int*)val;
+        return true;
+    }
     if (name == "use_tbb" && type == TypeInt) {
         oiio_use_tbb = *(const int*)val;
         return true;
@@ -472,6 +477,10 @@ getattribute(string_view name, TypeDesc type, void* val)
         *(int*)val = dds_bc5normal;
         return true;
     }
+    if (name == "imagebuf:print_uncaught_errors" && type == TypeInt) {
+        *(int*)val = imagebuf_print_uncaught_errors;
+        return true;
+    }
     if (name == "use_tbb" && type == TypeInt) {
         *(int*)val = oiio_use_tbb;
         return true;

src/libOpenImageIO/imageio_pvt.h.in

@@ -44,6 +44,7 @@ extern int openexr_core;
 extern int limit_channels;
 extern int limit_imagesize_MB;
 extern int opencv_version;
+extern int imagebuf_print_uncaught_errors;
 extern OIIO_UTIL_API int oiio_use_tbb; // This lives in libOpenImageIO_Util
 OIIO_API const std::vector<std::string>& font_dirs();
 OIIO_API const std::vector<std::string>& font_file_list();