common: add system-level config file (#26118)

* common: Add CLI > ENV > models-presets > INI precedence

1. CLI flags have the highest precedence
2. ENV vars have the second-highest precedence
3. System and User configs have the lowest precedence
   - Linux/BSD/Mac
     - /etc/llama.cpp/config.ini < ${XDG_CONFIG_HOME:-~/.config}/llama.cpp/config.ini
   - Windows
     - %PROGRAMDATA%\llama.cpp\config.ini < %APPDATA%\llama.cpp\config.ini

* fix UB

* use common_get_env

* ignore_unknown_keys

* nits

* add docs

---------

Co-authored-by: Xuan Son Nguyen <son@huggingface.co>

common/arg.cpp

@@ -35,6 +35,7 @@
 #include <regex>
 #include <set>
 #include <string>
+#include <system_error>
 #include <thread> // for hardware_concurrency
 #include <vector>
 
@@ -704,12 +705,61 @@ void common_models_handler_apply(common_models_handler & handler, common_params
 // CLI argument parsing functions
 //
 
+// apply config files (if present), a later file overrides an earlier one:
+// 1. system-wide: /etc/llama.cpp/config.ini (%PROGRAMDATA%\llama.cpp\config.ini on windows)
+// 2. user-level: ${XDG_CONFIG_HOME:-~/.config}/llama.cpp/config.ini (%APPDATA%\llama.cpp\config.ini on windows)
+static void common_params_apply_system_config(common_params & params, llama_example ex) {
+    std::vector<std::string> paths;
+
+#if defined(_WIN32)
+    const std::string program_data = common_get_env("PROGRAMDATA");
+    if (!program_data.empty()) {
+        paths.push_back(program_data + "\\llama.cpp\\config.ini");
+    }
+#else
+    paths.push_back("/etc/llama.cpp/config.ini");
+#endif
+
+    try {
+        paths.push_back(fs_get_config_directory() + "config.ini");
+    } catch (const std::exception & e) {
+        LOG_DBG("cannot read user-level config file, skipping: %s\n", e.what());
+    }
+
+    std::vector<std::string> found;
+    for (const auto & path : paths) {
+        std::error_code ec;
+        if (std::filesystem::exists(path, ec)) {
+            found.push_back(path);
+        }
+    }
+    if (found.empty()) {
+        return;
+    }
+
+    common_preset_context ctx(ex);
+    ctx.ignore_unknown_keys = true; // the same config file is shared by all programs
+    for (const auto & path : found) {
+        LOG_INF("using config file: %s\n", path.c_str());
+        common_preset global;
+        common_presets presets = ctx.load_from_ini(path, global);
+        global.apply_to_params(params);
+        auto it = presets.find(COMMON_PRESET_DEFAULT_NAME);
+        if (it != presets.end()) {
+            it->second.apply_to_params(params);
+        }
+    }
+}
+
 static bool common_params_parse_ex(int argc, char ** argv, common_params_context & ctx_arg) {
     common_params & params = ctx_arg.params;
 
     // setup log directly from params.verbosity: see tools/cli/cli.cpp
     common_log_set_verbosity_thold(params.verbosity);
 
+    // config file applies first, so env variables and CLI arguments override it
+    common_params_apply_system_config(params, ctx_arg.ex);
+
     std::unordered_map<std::string, std::pair<common_arg *, bool>> arg_to_options;
     for (auto & opt : ctx_arg.options) {
         for (const auto & arg : opt.args) {

common/common.cpp

@@ -1019,20 +1019,21 @@ std::string fs_get_cache_directory() {
     std::string cache_directory = "";
     auto ensure_trailing_slash = [](std::string p) {
         // Make sure to add trailing slash
-        if (p.back() != DIRECTORY_SEPARATOR) {
+        if (p.empty() || p.back() != DIRECTORY_SEPARATOR) {
             p += DIRECTORY_SEPARATOR;
         }
         return p;
     };
-    if (getenv("LLAMA_CACHE")) {
-        cache_directory = std::getenv("LLAMA_CACHE");
-    } else {
+    cache_directory = common_get_env("LLAMA_CACHE");
+    if (cache_directory.empty()) {
 #if defined(__linux__) || defined(__FreeBSD__) || defined(_AIX) || \
         defined(__OpenBSD__) || defined(__NetBSD__)
-        if (std::getenv("XDG_CACHE_HOME")) {
-            cache_directory = std::getenv("XDG_CACHE_HOME");
-        } else if (std::getenv("HOME")) {
-            cache_directory = std::getenv("HOME") + std::string("/.cache/");
+        const std::string xdg_cache_home = common_get_env("XDG_CACHE_HOME");
+        const std::string home           = common_get_env("HOME");
+        if (!xdg_cache_home.empty()) {
+            cache_directory = xdg_cache_home;
+        } else if (!home.empty()) {
+            cache_directory = home + "/.cache/";
         } else {
 #if defined(__linux__)
             /* no $HOME is defined, fallback to getpwuid */
@@ -1047,9 +1048,16 @@ std::string fs_get_cache_directory() {
 #endif /* defined(__linux__) */
         }
 #elif defined(__APPLE__)
-        cache_directory = std::getenv("HOME") + std::string("/Library/Caches/");
+        cache_directory = common_get_env("HOME");
+        if (cache_directory.empty()) {
+            throw std::runtime_error("Failed to find $HOME directory");
+        }
+        cache_directory += "/Library/Caches/";
 #elif defined(_WIN32)
-        cache_directory = std::getenv("LOCALAPPDATA");
+        cache_directory = common_get_env("LOCALAPPDATA");
+        if (cache_directory.empty()) {
+            throw std::runtime_error("Failed to find %LOCALAPPDATA% directory");
+        }
 #elif defined(__EMSCRIPTEN__)
         GGML_ABORT("not implemented on this platform");
 #else
@@ -1061,6 +1069,51 @@ std::string fs_get_cache_directory() {
     return ensure_trailing_slash(cache_directory);
 }
 
+std::string fs_get_config_directory() {
+    std::string config_directory = "";
+    auto ensure_trailing_slash = [](std::string p) {
+        if (p.empty() || p.back() != DIRECTORY_SEPARATOR) {
+            p += DIRECTORY_SEPARATOR;
+        }
+        return p;
+    };
+#if defined(__linux__) || defined(__FreeBSD__) || defined(_AIX) || \
+        defined(__OpenBSD__) || defined(__NetBSD__) || defined(__APPLE__)
+    const std::string xdg_config_home = common_get_env("XDG_CONFIG_HOME");
+    const std::string home            = common_get_env("HOME");
+    if (!xdg_config_home.empty()) {
+        config_directory = xdg_config_home;
+    } else if (!home.empty()) {
+        config_directory = home + "/.config/";
+    } else {
+#if defined(__linux__)
+        /* no $HOME is defined, fallback to getpwuid */
+        struct passwd *pw = getpwuid(getuid());
+        if ((!pw) || (!pw->pw_dir)) {
+            throw std::runtime_error("Failed to find $HOME directory");
+        }
+
+        config_directory = std::string(pw->pw_dir) + std::string("/.config/");
+#else
+        throw std::runtime_error("Failed to find $HOME directory");
+#endif
+    }
+#elif defined(_WIN32)
+    config_directory = common_get_env("APPDATA");
+    if (config_directory.empty()) {
+        throw std::runtime_error("Failed to find %APPDATA% directory");
+    }
+#elif defined(__EMSCRIPTEN__)
+    // caller decides what to do when there is no config directory
+    throw std::runtime_error("not implemented on this platform");
+#else
+#  error Unknown architecture
+#endif
+    config_directory = ensure_trailing_slash(config_directory);
+    config_directory += "llama.cpp";
+    return ensure_trailing_slash(config_directory);
+}
+
 std::string fs_get_cache_file(const std::string & filename) {
     GGML_ASSERT(filename.find(DIRECTORY_SEPARATOR) == std::string::npos);
     std::string cache_directory = fs_get_cache_directory();

common/common.h

@@ -881,6 +881,7 @@ bool fs_is_directory(const std::string & path);
 
 std::string fs_get_cache_directory();
 std::string fs_get_cache_file(const std::string & filename);
+std::string fs_get_config_directory();
 
 struct common_file_info {
     std::string path;

common/preset.cpp

@@ -322,6 +322,8 @@ common_presets common_preset_context::load_from_ini(const std::string & path, co
                     preset.options[opt] = value;
                 }
                 LOG_DBG("accepted option: %s = %s\n", key.c_str(), preset.options[opt].c_str());
+            } else if (ignore_unknown_keys) {
+                LOG_WRN("ignoring option '%s' from %s: not supported by this program\n", key.c_str(), path.c_str());
             } else {
                 throw std::runtime_error(string_format(
                     "option '%s' not recognized in preset '%s'",

common/preset.h

@@ -59,6 +59,10 @@ struct common_preset_context {
     bool filter_allowed_keys = false;
     std::set<std::string> allowed_keys;
 
+    // if true, options unknown to the current example are skipped instead of being an error
+    // used for config files shared by all binaries, where each binary only knows a subset of options
+    bool ignore_unknown_keys = false;
+
     // if only_remote_allowed is true, only accept whitelisted keys
     common_preset_context(llama_example ex);