build(deps): Raise giflib minimum to 5.0 (#4349)

Even that is quite old -- released in 2012! But it's the first version
that guaranteed thread safety for error reporting. So we're finally
making that our minimum and taking out the locking we did on our side.

Signed-off-by: Larry Gritz <[email protected]>

INSTALL.md

@@ -56,8 +56,7 @@ NEW or CHANGED MINIMUM dependencies since the last major release are **bold**.
    or for capturing images from a camera:
      * **OpenCV 4.x** (tested through 4.10)
  * If you want support for GIF images:
-     * giflib >= 4.1 (tested through 5.2; 5.0+ is strongly recommended for
-       stability and thread safety)
+     * **giflib >= 5.0** (tested through 5.2)
  * If you want support for HEIF/HEIC or AVIF images:
      * libheif >= 1.3 (1.7 required for AVIF support, 1.16 required for
        correct orientation support, tested through 1.17.6)

src/cmake/externalpackages.cmake

@@ -162,10 +162,8 @@ checked_find_package (TBB 2017
 checked_find_package (DCMTK CONFIG VERSION_MIN 3.6.1)
 
 checked_find_package (FFmpeg VERSION_MIN 4.0)
-checked_find_package (GIF
-                      VERSION_MIN 4
-                      RECOMMEND_MIN 5.0
-                      RECOMMEND_MIN_REASON "for stability and thread safety")
+
+checked_find_package (GIF VERSION_MIN 5.0)
 
 # For HEIF/HEIC/AVIF formats
 checked_find_package (Libheif VERSION_MIN 1.3

src/gif.imageio/gifinput.cpp

@@ -19,7 +19,7 @@
 
 // for older giflib versions
 #ifndef GIFLIB_MAJOR
-#    define GIFLIB_MAJOR 4
+#    error "GIFLIB 5.0 minimum required"
 #endif
 
 #ifndef DISPOSAL_UNSPECIFIED
@@ -132,12 +132,8 @@ OIIO_EXPORT const char* gif_input_extensions[] = { "gif", NULL };
 OIIO_EXPORT const char*
 gif_imageio_library_version()
 {
-#if defined(GIFLIB_MAJOR) && defined(GIFLIB_MINOR) && defined(GIFLIB_RELEASE)
     return "gif_lib " OIIO_STRINGIZE(GIFLIB_MAJOR) "." OIIO_STRINGIZE(
         GIFLIB_MINOR) "." OIIO_STRINGIZE(GIFLIB_RELEASE);
-#else
-    return "gif_lib unknown version";
-#endif
 }
 
 OIIO_PLUGIN_EXPORTS_END
@@ -408,20 +404,12 @@ GIFInput::seek_subimage(int subimage, int miplevel)
     if (!m_gif_file) {
         if (!ioproxy_use_or_open(m_filename))
             return false;
-#if GIFLIB_MAJOR >= 5
         int giflib_error;
         m_gif_file = DGifOpen(this, readFunc, &giflib_error);
         if (!m_gif_file) {
             errorfmt("{}", GifErrorString(giflib_error));
             return false;
         }
-#else
-        m_gif_file = DGifOpen(this, readFunc);
-        if (!m_gif_file) {
-            errorfmt("Error opening GIF");
-            return false;
-        }
-#endif
         m_subimage = -1;
         m_canvas.resize(m_gif_file->SWidth * m_gif_file->SHeight * 4);
     }
@@ -459,27 +447,12 @@ GIFInput::seek_subimage(int subimage, int miplevel)
 
 
 
-static spin_mutex gif_error_mutex;
-
-
 void
 GIFInput::report_last_error(void)
 {
-    // N.B. Only GIFLIB_MAJOR >= 5 looks properly thread-safe, in that the
-    // error is guaranteed to be specific to this open file.  We use a  spin
-    // mutex to prevent a thread clash for older versions, but it still
-    // appears to be a global call, so we can't be absolutely sure that the
-    // error was for *this* file.  So if you're using giflib prior to
-    // version 5, beware.
-#if GIFLIB_MAJOR >= 5
+    // GIFLIB_MAJOR >= 5 looks properly thread-safe, in that the error is
+    // guaranteed to be specific to this open file.
     errorfmt("{}", GifErrorString(m_gif_file->Error));
-#elif GIFLIB_MAJOR == 4 && GIFLIB_MINOR >= 2
-    spin_lock lock(gif_error_mutex);
-    errorfmt("{}", GifErrorString());
-#else
-    spin_lock lock(gif_error_mutex);
-    errorfmt("GIF error {}", GifLastError());
-#endif
 }