fix: fix possible fmt exceptions where we might have passed null string (AcademySoftwareFoundation#5115)

I've heard occasional reports of uncaught exceptions in print
statements. I haven't caught it in the act yet, but one set of reports
involved the following output:

OpenImageIO/detail/fmt/format-inl.h:40: assertion failed: string pointer
is null

So I'm proactively trying to find places that might be passing a null as
a string. I'm just guessing here, but these are plausible candidates.

---------

Signed-off-by: Larry Gritz <lg@larrygritz.com>
Signed-off-by: Vlad (Kuzmin) Erium <libalias@gmail.com>
Signed-off-by: Vlad <shaamaan@gmail.com>

Author: lgritz

src/libutil/strutil_test.cpp

@@ -1328,6 +1328,14 @@ test_string_view()
     Strutil::print("addr cstr={:p}, s={:p}, ustring={:p}, sr={:p}, c_str(sr)={:p}\n",
                      (void*)cstr, (void*)s.c_str(), (void*)ustring(cstr).c_str(), (void*)sr.data(),
                      (void*)OIIO::c_str(sr));
+
+    // Test some edge cases for fmt formatting
+    string_view empty(""), uninit;
+    Strutil::print("Test print empty string_view: '{}'\n", empty);
+    Strutil::print("Test print default initialized string_view: '{}'\n", uninit);
+    OIIO_CHECK_EQUAL(empty, uninit);
+    OIIO_CHECK_EQUAL(Strutil::format("{}", empty),
+                     Strutil::format("{}", uninit));
 }
 
 

src/libutil/ustring_test.cpp

@@ -167,6 +167,12 @@ test_ustring()
     OIIO_CHECK_EQUAL(whichtype, ustring("foo"));
     OIIO_CHECK_ASSERT((std::is_same<decltype(whichtype), ustring>::value));
     OIIO_CHECK_ASSERT(!(std::is_same<decltype(whichtype), const char*>::value));
+
+    // Test some edge cases for fmt formatting
+    Strutil::print("Test print empty ustring: '{}'\n", empty);
+    Strutil::print("Test print default initialized ustring: '{}'\n", uninit);
+    OIIO_CHECK_EQUAL(Strutil::format("{}", empty),
+                     Strutil::format("{}", uninit));
 }
 
 

src/raw.imageio/rawinput.cpp

@@ -425,16 +425,18 @@ RawInput::open_raw(bool unpack, bool process, const std::string& name,
     int ret = m_processor->open_file(name.c_str());
 #endif
     if (ret != LIBRAW_SUCCESS) {
+        const char* err = libraw_strerror(ret);
         errorfmt("Could not open file \"{}\", {}", m_filename,
-                 libraw_strerror(ret));
+                 err ? err : "unknown error");
         return false;
     }
 
     OIIO_ASSERT(!m_unpacked);
     if (unpack) {
         if ((ret = m_processor->unpack()) != LIBRAW_SUCCESS) {
+            const char* err = libraw_strerror(ret);
             errorfmt("Could not unpack \"{}\", {}", m_filename,
-                     libraw_strerror(ret));
+                     err ? err : "unknown error");
             return false;
         }
         m_unpacked = true;
@@ -912,13 +914,16 @@ RawInput::open_raw(bool unpack, bool process, const std::string& name,
             // Get unadjusted max value (need to force a read first)
             ret = m_processor->raw2image_ex(/*subtract_black=*/true);
             if (ret != LIBRAW_SUCCESS) {
-                errorfmt("HighlightMode adjustment detection read failed");
-                errorfmt("{}", libraw_strerror(ret));
+                const char* err = libraw_strerror(ret);
+                errorfmt("HighlightMode adjustment detection read failed ({})",
+                         err ? err : "unknown error");
                 return false;
             }
-            if (m_processor->adjust_maximum() != LIBRAW_SUCCESS) {
-                errorfmt("HighlightMode minimum adjustment failed");
-                errorfmt("{}", libraw_strerror(ret));
+            ret = m_processor->adjust_maximum();
+            if (ret != LIBRAW_SUCCESS) {
+                const char* err = libraw_strerror(ret);
+                errorfmt("HighlightMode minimum adjustment failed ({})",
+                         err ? err : "unknown error");
                 return false;
             }
             float unadjusted = m_processor->imgdata.color.maximum;
@@ -928,9 +933,11 @@ RawInput::open_raw(bool unpack, bool process, const std::string& name,
                 = (old_max_thr == 0.0f) ? 1.0 : old_max_thr;
 
             // Get new max value
-            if (m_processor->adjust_maximum() != LIBRAW_SUCCESS) {
-                errorfmt("HighlightMode maximum adjustment failed");
-                errorfmt("{}", libraw_strerror(ret));
+            ret = m_processor->adjust_maximum();
+            if (ret != LIBRAW_SUCCESS) {
+                const char* err = libraw_strerror(ret);
+                errorfmt("HighlightMode maximum adjustment failed ({})",
+                         err ? err : "unknown error");
                 return false;
             }
             float adjusted = m_processor->imgdata.color.maximum;
@@ -1566,7 +1573,9 @@ RawInput::do_process()
     if (!m_image) {
         int ret = m_processor->dcraw_process();
         if (ret != LIBRAW_SUCCESS) {
-            errorfmt("Processing image failed, {}", libraw_strerror(ret));
+            const char* err = libraw_strerror(ret);
+            errorfmt("Processing image failed, {}",
+                     err ? err : "unknown error");
             return false;
         }