Const correctness improvements:

removed some unnecessary const_casts that remove const.

src/PrusaSlicer.cpp

@@ -691,7 +691,7 @@ extern "C" {
         for (size_t i = 0; i < argc; ++ i)
             argv_narrow.emplace_back(boost::nowide::narrow(argv[i]));
         for (size_t i = 0; i < argc; ++ i)
-            argv_ptrs[i] = const_cast<char*>(argv_narrow[i].data());
+            argv_ptrs[i] = argv_narrow[i].data();
         // Call the UTF8 main.
         return CLI().run(argc, argv_ptrs.data());
     }

src/avrdude/avrdude-slic3r.cpp

@@ -93,11 +93,11 @@ void AvrDude::priv::unset_handlers()
 
 
 int AvrDude::priv::run_one(const std::vector<std::string> &args) {
-	std::vector<char*> c_args { const_cast<char*>(PACKAGE) };
+	std::vector<const char*> c_args { PACKAGE };
 	std::string command_line { PACKAGE };
 
 	for (const auto &arg : args) {
-		c_args.push_back(const_cast<char*>(arg.data()));
+		c_args.push_back(arg.c_str());
 		command_line.push_back(' ');
 		command_line.append(arg);
 	}
@@ -107,7 +107,7 @@ int AvrDude::priv::run_one(const std::vector<std::string> &args) {
 
 	message_fn(command_line.c_str(), (unsigned)command_line.size());
 
-	const auto res = ::avrdude_main(static_cast<int>(c_args.size()), c_args.data());
+	const auto res = ::avrdude_main(static_cast<int>(c_args.size()), const_cast<char**>(c_args.data()));
 
 	return res;
 }

src/libslic3r/Config.cpp

@@ -630,39 +630,38 @@ size_t ConfigBase::load_from_gcode_string(const char* str)
         return 0;
 
     // Walk line by line in reverse until a non-configuration key appears.
-    char *data_start = const_cast<char*>(str);
+    const char *data_start = str;
     // boost::nowide::ifstream seems to cook the text data somehow, so less then the 64k of characters may be retrieved.
-    char *end = data_start + strlen(str);
+    const char *end = data_start + strlen(str);
     size_t num_key_value_pairs = 0;
     for (;;) {
         // Extract next line.
         for (--end; end > data_start && (*end == '\r' || *end == '\n'); --end);
         if (end == data_start)
             break;
-        char *start = end;
+        const char *start = end ++;
-        *(++end) = 0;
         for (; start > data_start && *start != '\r' && *start != '\n'; --start);
         if (start == data_start)
             break;
         // Extracted a line from start to end. Extract the key = value pair.
         if (end - (++ start) < 10 || start[0] != ';' || start[1] != ' ')
             break;
-        char *key = start + 2;
+        const char *key = start + 2;
         if (!(*key >= 'a' && *key <= 'z') || (*key >= 'A' && *key <= 'Z'))
             // A key must start with a letter.
             break;
-        char *sep = strchr(key, '=');
+        const char *sep = key;
-        if (sep == nullptr || sep[-1] != ' ' || sep[1] != ' ')
+        for (; sep != end && *sep != '='; ++ sep) ;
+        if (sep == end || sep[-1] != ' ' || sep[1] != ' ')
             break;
-        char *value = sep + 2;
+        const char *value = sep + 2;
         if (value > end)
             break;
-        char *key_end = sep - 1;
+        const char *key_end = sep - 1;
         if (key_end - key < 3)
             break;
-        *key_end = 0;
         // The key may contain letters, digits and underscores.
-        for (char *c = key; c != key_end; ++c)
+        for (const char *c = key; c != key_end; ++ c)
             if (!((*c >= 'a' && *c <= 'z') || (*c >= 'A' && *c <= 'Z') || (*c >= '0' && *c <= '9') || *c == '_')) {
                 key = nullptr;
                 break;
@@ -670,7 +669,7 @@ size_t ConfigBase::load_from_gcode_string(const char* str)
         if (key == nullptr)
             break;
         try {
-            this->set_deserialize(key, value);
+            this->set_deserialize(std::string(key, key_end), std::string(value, end));
             ++num_key_value_pairs;
         }
         catch (UnknownOptionException & /* e */) {
@@ -760,15 +759,15 @@ ConfigOption* DynamicConfig::optptr(const t_config_option_key &opt_key, bool cre
 
 void DynamicConfig::read_cli(const std::vector<std::string> &tokens, t_config_option_keys* extra, t_config_option_keys* keys)
 {
-    std::vector<char*> args;    
+    std::vector<const char*> args;    
     // push a bogus executable name (argv[0])
-    args.emplace_back(const_cast<char*>(""));
+    args.emplace_back("");
     for (size_t i = 0; i < tokens.size(); ++ i)
-        args.emplace_back(const_cast<char *>(tokens[i].c_str()));
+        args.emplace_back(tokens[i].c_str());
-    this->read_cli(int(args.size()), &args[0], extra, keys);
+    this->read_cli(int(args.size()), args.data(), extra, keys);
 }
 
-bool DynamicConfig::read_cli(int argc, char** argv, t_config_option_keys* extra, t_config_option_keys* keys)
+bool DynamicConfig::read_cli(int argc, const char* const argv[], t_config_option_keys* extra, t_config_option_keys* keys)
 {
     // cache the CLI option => opt_key mapping
     std::map<std::string,std::string> opts;

src/libslic3r/Config.hpp

@@ -1779,7 +1779,7 @@ public:
 
     // Command line processing
     void                read_cli(const std::vector<std::string> &tokens, t_config_option_keys* extra, t_config_option_keys* keys = nullptr);
-    bool                read_cli(int argc, char** argv, t_config_option_keys* extra, t_config_option_keys* keys = nullptr);
+    bool                read_cli(int argc, const char* const argv[], t_config_option_keys* extra, t_config_option_keys* keys = nullptr);
 
     std::map<t_config_option_key, std::unique_ptr<ConfigOption>>::const_iterator cbegin() const { return options.cbegin(); }
     std::map<t_config_option_key, std::unique_ptr<ConfigOption>>::const_iterator cend()   const { return options.cend(); }

src/libslic3r/Format/AMF.cpp

@@ -683,7 +683,7 @@ void AMFParserContext::endElement(const char * /* name */)
                     config->set_deserialize(opt_key, m_value[1]);
             } else if (m_path.size() == 3 && m_path[1] == NODE_TYPE_OBJECT && m_object && strcmp(opt_key, "layer_height_profile") == 0) {
                 // Parse object's layer height profile, a semicolon separated list of floats.
-                char *p = const_cast<char*>(m_value[1].c_str());
+                char *p = m_value[1].data();
                 for (;;) {
                     char *end = strchr(p, ';');
                     if (end != nullptr)
@@ -698,7 +698,7 @@ void AMFParserContext::endElement(const char * /* name */)
                 // Parse object's layer height profile, a semicolon separated list of floats.
                 unsigned char coord_idx = 0;
                 Eigen::Matrix<float, 5, 1, Eigen::DontAlign> point(Eigen::Matrix<float, 5, 1, Eigen::DontAlign>::Zero());
-                char *p = const_cast<char*>(m_value[1].c_str());
+                char *p = m_value[1].data();
                 for (;;) {
                     char *end = strchr(p, ';');
                     if (end != nullptr)
@@ -718,7 +718,7 @@ void AMFParserContext::endElement(const char * /* name */)
             else if (m_path.size() == 5 && m_path[1] == NODE_TYPE_OBJECT && m_path[3] == NODE_TYPE_RANGE && 
                      m_object && strcmp(opt_key, "layer_height_range") == 0) {
                 // Parse object's layer_height_range, a semicolon separated doubles.
-                char* p = const_cast<char*>(m_value[1].c_str());
+                char* p = m_value[1].data();
                 char* end = strchr(p, ';');
                 *end = 0;
 
@@ -1010,7 +1010,7 @@ bool load_amf(const char* path, DynamicPrintConfig* config, Model* model, bool c
             return false;
 
         std::string zip_mask(2, '\0');
-        file.read(const_cast<char*>(zip_mask.data()), 2);
+        file.read(zip_mask.data(), 2);
         file.close();
 
         return (zip_mask == "PK") ? load_amf_archive(path, config, model, check_version) : load_amf_file(path, config, model);

src/libslic3r/Format/objparser.cpp

@@ -420,7 +420,7 @@ bool loadvector(FILE *pFile, std::vector<std::string> &v)
 		if (::fread(&len, sizeof(len), 1, pFile) != 1)
 			return false;
 		std::string s(" ", len);
-		if (::fread(const_cast<char*>(s.c_str()), 1, len, pFile) != len)
+		if (::fread(s.data(), 1, len, pFile) != len)
 			return false;
 		v.push_back(std::move(s));
 	}
@@ -442,7 +442,7 @@ bool loadvectornameidx(FILE *pFile, std::vector<T> &v)
 		if (::fread(&len, sizeof(len), 1, pFile) != 1)
 			return false;
 		v[i].name.assign(" ", len);
-		if (::fread(const_cast<char*>(v[i].name.c_str()), 1, len, pFile) != len)
+		if (::fread(v[i].name.data(), 1, len, pFile) != len)
 			return false;
 	}
 	return true;

src/libslic3r/Semver.hpp

@@ -149,7 +149,7 @@ private:
 	Semver(semver_t ver) : ver(ver) {}
 
 	static semver_t semver_zero() { return { 0, 0, 0, nullptr, nullptr }; }
-	static char * strdup(const std::string &str) { return ::semver_strdup(const_cast<char*>(str.c_str())); }
+	static char * strdup(const std::string &str) { return ::semver_strdup(str.data()); }
 };
 
 

src/libslic3r/utils.cpp

@@ -535,7 +535,7 @@ std::string encode_path(const char *src)
     // Convert a wide string to a local code page.
     int size_needed = ::WideCharToMultiByte(0, 0, wstr_src.data(), (int)wstr_src.size(), nullptr, 0, nullptr, nullptr);
     std::string str_dst(size_needed, 0);
-    ::WideCharToMultiByte(0, 0, wstr_src.data(), (int)wstr_src.size(), const_cast<char*>(str_dst.data()), size_needed, nullptr, nullptr);
+    ::WideCharToMultiByte(0, 0, wstr_src.data(), (int)wstr_src.size(), str_dst.data(), size_needed, nullptr, nullptr);
     return str_dst;
 #else /* WIN32 */
     return src;
@@ -552,7 +552,7 @@ std::string decode_path(const char *src)
     // Convert the string encoded using the local code page to a wide string.
     int size_needed = ::MultiByteToWideChar(0, 0, src, len, nullptr, 0);
     std::wstring wstr_dst(size_needed, 0);
-    ::MultiByteToWideChar(0, 0, src, len, const_cast<wchar_t*>(wstr_dst.data()), size_needed);
+    ::MultiByteToWideChar(0, 0, src, len, wstr_dst.data(), size_needed);
     // Convert a wide string to utf8.
     return boost::nowide::narrow(wstr_dst.c_str());
 #else /* WIN32 */

src/slic3r/Config/Version.cpp

@@ -205,7 +205,7 @@ size_t Index::load(const boost::filesystem::path &path)
 #endif
     	++ idx_line;
     	// Skip the initial white spaces.
-    	char *key = left_trim(const_cast<char*>(line.data()));
+    	char *key = left_trim(line.data());
 		if (*key == '#')
 			// Skip a comment line.
 			continue;

src/slic3r/GUI/Camera.cpp

@@ -338,7 +338,7 @@ void Camera::debug_render() const
     float fov = (float)get_fov();
     float gui_scale = (float)get_gui_scale();
 
-    ImGui::InputText("Type", const_cast<char*>(type.data()), type.length(), ImGuiInputTextFlags_ReadOnly);
+    ImGui::InputText("Type", type.data(), type.length(), ImGuiInputTextFlags_ReadOnly);
     ImGui::Separator();
     ImGui::InputFloat3("Position", position.data(), "%.6f", ImGuiInputTextFlags_ReadOnly);
     ImGui::InputFloat3("Target", target.data(), "%.6f", ImGuiInputTextFlags_ReadOnly);

src/slic3r/GUI/GLShader.cpp

@@ -142,7 +142,7 @@ bool GLShader::load_from_file(const char* fragment_shader_filename, const char*
     int file_length = (int)vs.tellg();
     vs.seekg(0, vs.beg);
     std::string vertex_shader(file_length, '\0');
-    vs.read(const_cast<char*>(vertex_shader.data()), file_length);
+    vs.read(vertex_shader.data(), file_length);
     if (!vs.good())
         return false;
 
@@ -156,7 +156,7 @@ bool GLShader::load_from_file(const char* fragment_shader_filename, const char*
     file_length = (int)fs.tellg();
     fs.seekg(0, fs.beg);
     std::string fragment_shader(file_length, '\0');
-    fs.read(const_cast<char*>(fragment_shader.data()), file_length);
+    fs.read(fragment_shader.data(), file_length);
     if (!fs.good())
         return false;
 

src/slic3r/GUI/PresetBundle.cpp

@@ -560,9 +560,11 @@ DynamicPrintConfig PresetBundle::full_fff_config() const
 		while (filament_configs.size() < num_extruders)
             filament_configs.emplace_back(&this->filaments.first_visible().config);
         for (const DynamicPrintConfig *cfg : filament_configs) {
-            compatible_printers_condition.emplace_back(Preset::compatible_printers_condition(*const_cast<DynamicPrintConfig*>(cfg)));
+            // The compatible_prints/printers_condition() returns a reference to configuration key, which may not yet exist.
-            compatible_prints_condition  .emplace_back(Preset::compatible_prints_condition(*const_cast<DynamicPrintConfig*>(cfg)));
+            DynamicPrintConfig &cfg_rw = *const_cast<DynamicPrintConfig*>(cfg);
-            inherits                     .emplace_back(Preset::inherits(*const_cast<DynamicPrintConfig*>(cfg)));
+            compatible_printers_condition.emplace_back(Preset::compatible_printers_condition(cfg_rw));
+            compatible_prints_condition  .emplace_back(Preset::compatible_prints_condition(cfg_rw));
+            inherits                     .emplace_back(Preset::inherits(cfg_rw));
         }
         // Option values to set a ConfigOptionVector from.
         std::vector<const ConfigOption*> filament_opts(num_extruders, nullptr);

src/slic3r/GUI/RemovableDriveManager.cpp

@@ -325,7 +325,7 @@ void RemovableDriveManager::inspect_file(const std::string &path, const std::str
 			{
 				if(pw->pw_name == username)
 				{
-					std::string name = basename(const_cast<char*>(path.c_str()));
+					std::string name = basename(path.data());
 		       		m_current_drives.push_back(DriveData(name,path));
 				}
 			}