Fix new in clang 13.1 (Xcode13.3) warnings (KhronosGroup#553)

These are set-but-not-used warnings new in Xcode 13.3.

* Rationalize suppressions of old and new warnings

* Incidentally, fix build_wasm_docker.sh to use EXIT trap to ensure terminating the docker container.

CMakeLists.txt

@@ -148,16 +148,6 @@ elseif(${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU"
     add_compile_options(-Wall -Wextra)
     add_compile_options( $<IF:$<CONFIG:Debug>,-O0,-O3> )
     if(EMSCRIPTEN)
-        # For reasons I have yet to understand, the clang v12 used by the
-        # current Emscripten versions raises this deprecated copy warning on
-        # the assimp headers while the clang v12 used by Xcode does not. I am
-        # also unable to update the assimp headers as the macOS build of the
-        # matching version of libassimp fails. There has been no response
-        # from the assimp project and I don't have time to investigate.
-        # Therefore, since we don't have an Emscripten port of libassimp,
-        # meaning the relevant load tests will never be called, just globally
-        # suppress the warning.
-        add_compile_options(-Wno-deprecated-copy)
         add_link_options( $<IF:$<CONFIG:Debug>,-gsource-map,-O3> )
     else()
         add_link_options( $<IF:$<CONFIG:Debug>,-g,-O3> )
@@ -489,6 +479,10 @@ PRIVATE
 # Turn off these warnings until Rich fixes the occurences.
 # It it not clear to me if generator expressions can be used here
 # hence the long-winded way.
+#message(STATUS
+#        "CMAKE_CXX_COMPILER_ID = ${CMAKE_CXX_COMPILER_ID} "
+#        "CMAKE_CXX_COMPILER_VERSION = ${CMAKE_CXX_COMPILER_VERSION}"
+#)
 if(MSVC)
 # Currently no need to disable any warnings in basisu code. Rich fixed them.
 elseif(${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU")
@@ -497,34 +491,51 @@ elseif(${CMAKE_CXX_COMPILER_ID} STREQUAL "GNU")
         # disabled.
         ${BASISU_ENCODER_CXX_SRC}
         PROPERTIES COMPILE_OPTIONS "-Wno-sign-compare;-Wno-unused-variable;-Wno-class-memaccess;-Wno-misleading-indentation;-Wno-extra;-Wno-deprecated-copy;-Wno-parentheses;-Wno-strict-aliasing"
-        )
+    )
     set_source_files_properties(
         lib/basisu/transcoder/basisu_transcoder.cpp
         PROPERTIES COMPILE_OPTIONS "-Wno-sign-compare;-Wno-unused-function;-Wno-unused-variable;-Wno-class-memaccess;-Wno-maybe-uninitialized"
+    )
+    if (${CMAKE_CXX_COMPILER_VERSION} VERSION_GREATER_EQUAL "11.0")
+        set_source_files_properties(
+            lib/basisu/zstd/zstd.c
+            PROPERTIES COMPILE_OPTIONS "-Wno-unused-but-set-variable"
         )
-elseif(EMSCRIPTEN)
-    set_source_files_properties(
-        ${BASISU_ENCODER_CXX_SRC}
-        PROPERTIES COMPILE_OPTIONS "-Wno-sign-compare;-Wno-unused-variable;-Wno-unused-parameter;-Wno-unused-but-set-variable"
-        )
-    set_source_files_properties(
-        lib/basisu/transcoder/basisu_transcoder.cpp
-        PROPERTIES COMPILE_OPTIONS "-Wno-sign-compare;-Wno-unused-function;-Wno-unused-variable"
-        )
-    set_source_files_properties(
-        lib/basisu/zstd/zstd.c
-        PROPERTIES COMPILE_OPTIONS "-Wno-unused-but-set-variable;-Wno-bitwise-instead-of-logical"
-        )
+    endif()
 elseif(${CMAKE_CXX_COMPILER_ID} MATCHES "Clang")
-    #message(STATUS "CMAKE_CXX_COMPILER_VERSION = ${CMAKE_CXX_COMPILER_VERSION}")
     if (${CMAKE_CXX_COMPILER_VERSION} VERSION_GREATER_EQUAL "12.0.5")
         set_source_files_properties( lib/basisu/encoder/basisu_kernels_sse.cpp
             PROPERTIES COMPILE_OPTIONS "-Wno-unused-parameter;-Wno-deprecated-copy;-Wno-uninitialized-const-reference"
             )
     else()
         set_source_files_properties( lib/basisu/encoder/basisu_kernels_sse.cpp
             PROPERTIES COMPILE_OPTIONS "-Wno-unused-parameter"
-            )
+        )
+    endif()
+    if (${CMAKE_CXX_COMPILER_VERSION} VERSION_GREATER_EQUAL "13.1")
+        set_source_files_properties(
+            # We haven't fixed zstd.c because the fix would have to be applied
+            # every time the upstream script is used to create an updated
+            # single file decoder.
+            lib/basisu/zstd/zstd.c
+            PROPERTIES COMPILE_OPTIONS "-Wno-unused-but-set-variable"
+        )
+    endif()
+    if (${CMAKE_CXX_COMPILER_VERSION} VERSION_GREATER_EQUAL "15.0")
+        # These are for Emscripten which is ahead of xcode in its clang
+        # version. Also future proofing for when xcode catches up.
+        set_source_files_properties(
+            ${BASISU_ENCODER_CXX_SRC}
+            PROPERTIES COMPILE_OPTIONS "-Wno-sign-compare;-Wno-unused-variable;-Wno-unused-parameter"
+        )
+        set_source_files_properties(
+            lib/basisu/transcoder/basisu_transcoder.cpp
+            PROPERTIES COMPILE_OPTIONS "-Wno-sign-compare;-Wno-unused-function;-Wno-unused-variable"
+        )
+        set_source_files_properties(
+            lib/basisu/zstd/zstd.c
+            PROPERTIES COMPILE_OPTIONS "-Wno-unused-but-set-variable;-Wno-bitwise-instead-of-logical"
+        )
     endif()
 else()
     message(ERROR "${CMAKE_CXX_COMPILER_ID} not yet supported.")

lib/basisu/encoder/basisu_bc7enc.cpp

@@ -1281,6 +1281,15 @@ static uint64_t find_optimal_solution(uint32_t mode, bc7enc_vec4F xl, bc7enc_vec
 	return pResults->m_best_overall_err;
 }
 
+#if (__cplusplus >= 201703L)
+#define MAYBE_UNUSED [[maybe_unused]]
+#elif __GNUC__ || __clang__
+  #define MAYBE_UNUSED __attribute__((unused))
+#else
+  // VC++ has no equivalent
+  #define MAYBE_UNUSED
+#endif
+
 void check_best_overall_error(const color_cell_compressor_params *pParams, color_cell_compressor_results *pResults)
 {
 	const uint32_t n = pParams->m_num_selector_weights;
@@ -1301,12 +1310,12 @@ void check_best_overall_error(const color_cell_compressor_params *pParams, color
 		for (uint32_t c = 0; c < 4; c++)
 			colors[i].m_c[c] = (uint8_t)astc_interpolate_linear(colors[0].m_c[c], colors[n - 1].m_c[c], pParams->m_pSelector_weights[i]);
 
-	uint64_t total_err = 0;
+    MAYBE_UNUSED uint64_t total_err = 0;
 	for (uint32_t p = 0; p < pParams->m_num_pixels; p++)
 	{
 		const color_quad_u8 &orig = pParams->m_pPixels[p];
 		const color_quad_u8 &packed = colors[pResults->m_pSelectors[p]];
-				
+
 		if (pParams->m_has_alpha)
 			total_err += compute_color_distance_rgba(&orig, &packed, pParams->m_perceptual, pParams->m_weights);
 		else

lib/basisu/encoder/basisu_comp.cpp

@@ -1303,13 +1303,12 @@ namespace basisu
 
 		m_output_basis_file = comp_data;
 
-		uint32_t total_orig_pixels = 0, total_texels = 0, total_orig_texels = 0;
+		uint32_t total_orig_pixels = 0, total_orig_texels = 0;
 		for (uint32_t i = 0; i < m_slice_descs.size(); i++)
 		{
 			const basisu_backend_slice_desc& slice_desc = m_slice_descs[i];
 
 			total_orig_pixels += slice_desc.m_orig_width * slice_desc.m_orig_height;
-			total_texels += slice_desc.m_width * slice_desc.m_height;
 		}
 
 		m_basis_file_size = (uint32_t)comp_data.size();

lib/basisu/encoder/basisu_frontend.cpp

@@ -2346,8 +2346,6 @@ namespace basisu
 					if (!cluster_block_indices.size())
 						continue;
 
-					uint64_t overall_best_err = 0;
-
 					uint64_t total_err[4][4][4];
 					clear_obj(total_err);
 
@@ -2398,8 +2396,6 @@ namespace basisu
 							}
 
 							m_optimized_cluster_selectors[cluster_index].set_selector(x, y, best_sel);
-
-							overall_best_err += best_err;
 						} // x
 					} // y
 

lib/basisu/encoder/basisu_gpu_texture.cpp

@@ -1533,17 +1533,13 @@ namespace basisu
 			packed_uint<4> packed_img_size(img_size);
 			append_vector(ktx_data, (uint8_t *)&packed_img_size, sizeof(packed_img_size));
 
-			uint32_t bytes_written = 0;
-
 			for (uint32_t array_index = 0; array_index < maximum<uint32_t>(1, header.m_numberOfArrayElements); array_index++)
 			{
 				for (uint32_t face_index = 0; face_index < header.m_numberOfFaces; face_index++)
 				{
 					const gpu_image& img = gpu_images[cubemap_flag ? (array_index * 6 + face_index) : array_index][level_index];
 
 					append_vector(ktx_data, (uint8_t *)img.get_ptr(), img.get_size_in_bytes());
-
-					bytes_written += img.get_size_in_bytes();
 				}
 
 			} // array_index

lib/basisu/encoder/basisu_uastc_enc.cpp

@@ -383,13 +383,17 @@ namespace basisu
 			}
 		}
 
+#if UASTC_WRITE_MODE_DESCS
 		uint32_t total_endpoint_bits = 0;
+#endif
 
 		for (uint32_t i = 0; i < total_tq_values; i++)
 		{
 			const uint32_t num_bits = ep_trits ? 8 : 7;
 			uastc_write_bits(buf, block_bit_offset, tq_values[i], num_bits, "ETQ");
+#if UASTC_WRITE_MODE_DESCS
 			total_endpoint_bits += num_bits;
+#endif
 		}
 
 		if (tq_mul > 1)
@@ -414,20 +418,24 @@ namespace basisu
 					num_bits = 5;
 			}
 			uastc_write_bits(buf, block_bit_offset, tq_accum, num_bits, "ETQ");
+#if UASTC_WRITE_MODE_DESCS
 			total_endpoint_bits += num_bits;
+#endif
 		}
 
 		for (uint32_t i = 0; i < total_values; i++)
 		{
 			uastc_write_bits(buf, block_bit_offset, bit_values[i], ep_bits, "EBITS");
+#if UASTC_WRITE_MODE_DESCS
 			total_endpoint_bits += ep_bits;
+#endif
 		}
 
 #if UASTC_WRITE_MODE_DESCS
 		uint32_t weight_start = block_bit_offset;
+        uint32_t total_weight_bits = 0;
 #endif
 
-		uint32_t total_weight_bits = 0;
 		const uint32_t plane_shift = (total_planes == 2) ? 1 : 0;
 		for (uint32_t i = 0; i < 16 * total_planes; i++)
 		{
@@ -443,7 +451,9 @@ namespace basisu
 
 			uastc_write_bits(buf, block_bit_offset, weights[i], numbits, nullptr);
 
+#if UASTC_WRITE_MODE_DESCS
 			total_weight_bits += numbits;
+#endif
 		}
 
 #if UASTC_WRITE_MODE_DESCS

lib/etcdec.cxx

@@ -177,9 +177,7 @@ submitted to the exclusive jurisdiction of the Swedish Courts.
 #elif __clang__
   #pragma clang diagnostic push
   #pragma clang diagnostic ignored "-Wunused-parameter"
-  #if defined(EMSCRIPTEN)
-    // Emscripten 3.1.6 lang warns this but not clang 13 in Xcode and Xcode
-    // warns no such warning group if this is set, hence the extra ifdef.
+  #if __clang_major__ > 13 || (__clang_major__ == 13 && __clang_minor__ >= 1)
     #pragma clang diagnostic ignored "-Wunused-but-set-variable"
   #endif
 #elif __GNUC__