Move /src to /subprojects

This will facilitate breaking up Nix into multiple packages for each
component with Meson.

subprojects/libutil-c/.version

@@ -0,0 +1 @@
+../../.version

subprojects/libutil-c/build-utils-meson

@@ -0,0 +1 @@
+../../build-utils-meson

subprojects/libutil-c/local.mk

@@ -0,0 +1,18 @@
+libraries += libutilc
+
+libutilc_NAME = libnixutilc
+
+libutilc_DIR := $(d)
+
+libutilc_SOURCES := $(wildcard $(d)/*.cc)
+
+# Not just for this library itself, but also for downstream libraries using this library
+
+INCLUDE_libutilc := -I $(d)
+libutilc_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libutilc)
+
+libutilc_LIBS = libutil
+
+libutilc_LDFLAGS += $(THREAD_LDFLAGS)
+
+libutilc_FORCE_INSTALL := 1

subprojects/libutil-c/meson.build

@@ -0,0 +1,81 @@
+project('nix-util-c', 'cpp',
+  version : files('.version'),
+  default_options : [
+    'cpp_std=c++2a',
+    # TODO(Qyriad): increase the warning level
+    'warning_level=1',
+    'debug=true',
+    'optimization=2',
+    'errorlogs=true', # Please print logs for tests that fail
+  ],
+  meson_version : '>= 1.1',
+  license : 'LGPL-2.1-or-later',
+)
+
+cxx = meson.get_compiler('cpp')
+
+subdir('build-utils-meson/deps-lists')
+
+configdata = configuration_data()
+
+deps_private_maybe_subproject = [
+  dependency('nix-util'),
+]
+deps_public_maybe_subproject = [
+]
+subdir('build-utils-meson/subprojects')
+
+subdir('build-utils-meson/threads')
+
+# TODO rename, because it will conflict with downstream projects
+configdata.set_quoted('PACKAGE_VERSION', meson.project_version())
+
+config_h = configure_file(
+  configuration : configdata,
+  output : 'config-util.h',
+)
+
+add_project_arguments(
+  # TODO(Qyriad): Yes this is how the autoconf+Make system did it.
+  # It would be nice for our headers to be idempotent instead.
+
+  # From C++ libraries, only for internals
+  '-include', 'config-util.hh',
+
+  # From C libraries, for our public, installed headers too
+  '-include', 'config-util.h',
+  language : 'cpp',
+)
+
+subdir('build-utils-meson/diagnostics')
+
+sources = files(
+  'nix_api_util.cc',
+)
+
+include_dirs = [include_directories('.')]
+
+headers = [config_h] + files(
+  'nix_api_util.h',
+)
+
+# TODO don't install this once tests don't use it.
+headers += files('nix_api_util_internal.h')
+
+subdir('build-utils-meson/export-all-symbols')
+
+this_library = library(
+  'nixutilc',
+  sources,
+  dependencies : deps_public + deps_private + deps_other,
+  include_directories : include_dirs,
+  link_args: linker_export_flags,
+  prelink : true, # For C++ static initializers
+  install : true,
+)
+
+install_headers(headers, subdir : 'nix', preserve_path : true)
+
+libraries_private = []
+
+subdir('build-utils-meson/export')

subprojects/libutil-c/meson.options

@@ -0,0 +1 @@
+# vim: filetype=meson

subprojects/libutil-c/nix-util-c.pc.in

@@ -0,0 +1,9 @@
+prefix=@prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: Nix libutil C API
+Description: Common functions for the Nix C API, such as error handling
+Version: @PACKAGE_VERSION@
+Libs: -L${libdir} -lnixutil
+Cflags: -I${includedir}/nix -std=c++2a

subprojects/libutil-c/nix_api_util.cc

@@ -0,0 +1,156 @@
+#include "nix_api_util.h"
+#include "config-global.hh"
+#include "error.hh"
+#include "nix_api_util_internal.h"
+#include "util.hh"
+
+#include <cxxabi.h>
+#include <typeinfo>
+
+nix_c_context * nix_c_context_create()
+{
+    return new nix_c_context();
+}
+
+void nix_c_context_free(nix_c_context * context)
+{
+    delete context;
+}
+
+nix_err nix_context_error(nix_c_context * context)
+{
+    if (context == nullptr) {
+        throw;
+    }
+    try {
+        throw;
+    } catch (nix::Error & e) {
+        /* Storing this exception is annoying, take what we need here */
+        context->last_err = e.what();
+        context->info = e.info();
+        int status;
+        const char * demangled = abi::__cxa_demangle(typeid(e).name(), 0, 0, &status);
+        if (demangled) {
+            context->name = demangled;
+            // todo: free(demangled);
+        } else {
+            context->name = typeid(e).name();
+        }
+        context->last_err_code = NIX_ERR_NIX_ERROR;
+        return context->last_err_code;
+    } catch (const std::exception & e) {
+        context->last_err = e.what();
+        context->last_err_code = NIX_ERR_UNKNOWN;
+        return context->last_err_code;
+    }
+    // unreachable
+}
+
+nix_err nix_set_err_msg(nix_c_context * context, nix_err err, const char * msg)
+{
+    if (context == nullptr) {
+        // todo last_err_code
+        throw nix::Error("Nix C api error: %s", msg);
+    }
+    context->last_err_code = err;
+    context->last_err = msg;
+    return err;
+}
+
+void nix_clear_err(nix_c_context * context)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+}
+
+const char * nix_version_get()
+{
+    return PACKAGE_VERSION;
+}
+
+// Implementations
+
+nix_err nix_setting_get(nix_c_context * context, const char * key, nix_get_string_callback callback, void * user_data)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    try {
+        std::map<std::string, nix::AbstractConfig::SettingInfo> settings;
+        nix::globalConfig.getSettings(settings);
+        if (settings.contains(key)) {
+            return call_nix_get_string_callback(settings[key].value, callback, user_data);
+        } else {
+            return nix_set_err_msg(context, NIX_ERR_KEY, "Setting not found");
+        }
+    }
+    NIXC_CATCH_ERRS
+}
+
+nix_err nix_setting_set(nix_c_context * context, const char * key, const char * value)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    if (nix::globalConfig.set(key, value))
+        return NIX_OK;
+    else {
+        return nix_set_err_msg(context, NIX_ERR_KEY, "Setting not found");
+    }
+}
+
+nix_err nix_libutil_init(nix_c_context * context)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    try {
+        nix::initLibUtil();
+        return NIX_OK;
+    }
+    NIXC_CATCH_ERRS
+}
+
+const char * nix_err_msg(nix_c_context * context, const nix_c_context * read_context, unsigned int * n)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    if (read_context->last_err && read_context->last_err_code != NIX_OK) {
+        if (n)
+            *n = read_context->last_err->size();
+        return read_context->last_err->c_str();
+    }
+    nix_set_err_msg(context, NIX_ERR_UNKNOWN, "No error message");
+    return nullptr;
+}
+
+nix_err nix_err_name(
+    nix_c_context * context, const nix_c_context * read_context, nix_get_string_callback callback, void * user_data)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    if (read_context->last_err_code != NIX_ERR_NIX_ERROR) {
+        return nix_set_err_msg(context, NIX_ERR_UNKNOWN, "Last error was not a nix error");
+    }
+    return call_nix_get_string_callback(read_context->name, callback, user_data);
+}
+
+nix_err nix_err_info_msg(
+    nix_c_context * context, const nix_c_context * read_context, nix_get_string_callback callback, void * user_data)
+{
+    if (context)
+        context->last_err_code = NIX_OK;
+    if (read_context->last_err_code != NIX_ERR_NIX_ERROR) {
+        return nix_set_err_msg(context, NIX_ERR_UNKNOWN, "Last error was not a nix error");
+    }
+    return call_nix_get_string_callback(read_context->info->msg.str(), callback, user_data);
+}
+
+nix_err nix_err_code(const nix_c_context * read_context)
+{
+    return read_context->last_err_code;
+}
+
+// internal
+nix_err call_nix_get_string_callback(const std::string str, nix_get_string_callback callback, void * user_data)
+{
+    callback(str.c_str(), str.size(), user_data);
+    return NIX_OK;
+}

subprojects/libutil-c/nix_api_util.h

@@ -0,0 +1,329 @@
+#ifndef NIX_API_UTIL_H
+#define NIX_API_UTIL_H
+/**
+ * @defgroup libutil libutil
+ * @brief C bindings for nix libutil
+ *
+ * libutil is used for functionality shared between
+ * different Nix modules.
+ * @{
+ */
+/** @file
+ * @brief Main entry for the libutil C bindings
+ *
+ * Also contains error handling utilities
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+// cffi start
+
+/** @defgroup errors Handling errors
+ * @brief Dealing with errors from the Nix side
+ *
+ * To handle errors that can be returned from the Nix API,
+ * a nix_c_context can be passed to any function that potentially returns an
+ * error.
+ *
+ * Error information will be stored in this context, and can be retrieved
+ * using nix_err_code and nix_err_msg.
+ *
+ * Passing NULL instead will cause the API to throw C++ errors.
+ *
+ * Example:
+ * @code{.c}
+ * int main() {
+ *     nix_c_context* ctx = nix_c_context_create();
+ *     nix_libutil_init(ctx);
+ *     if (nix_err_code(ctx) != NIX_OK) {
+ *         printf("error: %s\n", nix_err_msg(NULL, ctx, NULL));
+ *         return 1;
+ *     }
+ *     return 0;
+ * }
+ * @endcode
+ *  @{
+ */
+// Error codes
+/**
+ * @brief Type for error codes in the NIX system
+ *
+ * This type can have one of several predefined constants:
+ * - NIX_OK: No error occurred (0)
+ * - NIX_ERR_UNKNOWN: An unknown error occurred (-1)
+ * - NIX_ERR_OVERFLOW: An overflow error occurred (-2)
+ * - NIX_ERR_KEY: A key error occurred (-3)
+ * - NIX_ERR_NIX_ERROR: A generic Nix error occurred (-4)
+ */
+enum nix_err {
+
+    /**
+     * @brief No error occurred.
+     *
+     * This error code is returned when no error has occurred during the function
+     * execution.
+     */
+    NIX_OK = 0,
+
+    /**
+     * @brief An unknown error occurred.
+     *
+     * This error code is returned when an unknown error occurred during the
+     * function execution.
+     */
+    NIX_ERR_UNKNOWN = -1,
+
+    /**
+     * @brief An overflow error occurred.
+     *
+     * This error code is returned when an overflow error occurred during the
+     * function execution.
+     */
+    NIX_ERR_OVERFLOW = -2,
+
+    /**
+     * @brief A key error occurred.
+     *
+     * This error code is returned when a key error occurred during the function
+     * execution.
+     */
+    NIX_ERR_KEY = -3,
+
+    /**
+     * @brief A generic Nix error occurred.
+     *
+     * This error code is returned when a generic Nix error occurred during the
+     * function execution.
+     */
+    NIX_ERR_NIX_ERROR = -4,
+
+};
+
+typedef enum nix_err nix_err;
+
+/**
+ * @brief This object stores error state.
+ * @struct nix_c_context
+ *
+ * Passed as a first parameter to functions that can fail, to store error
+ * information.
+ *
+ * Optional wherever it can be used, passing NULL instead will throw a C++
+ * exception.
+ *
+ * The struct is laid out so that it can also be cast to nix_err* to inspect
+ * directly:
+ * @code{.c}
+ * assert(*(nix_err*)ctx == NIX_OK);
+ * @endcode
+ * @note These can be reused between different function calls,
+ *  but make sure not to use them for multiple calls simultaneously (which can
+ * happen in callbacks).
+ */
+typedef struct nix_c_context nix_c_context;
+
+/**
+ * @brief Called to get the value of a string owned by Nix.
+ *
+ * @param[in] start the string to copy.
+ * @param[in] n the string length.
+ * @param[in] user_data optional, arbitrary data, passed to the nix_get_string_callback when it's called.
+ */
+typedef void (*nix_get_string_callback)(const char * start, unsigned int n, void * user_data);
+
+// Function prototypes
+
+/**
+ * @brief Allocate a new nix_c_context.
+ * @throws std::bad_alloc
+ * @return allocated nix_c_context, owned by the caller. Free using
+ * `nix_c_context_free`.
+ */
+nix_c_context * nix_c_context_create();
+/**
+ * @brief Free a nix_c_context. Does not fail.
+ * @param[out] context The context to free, mandatory.
+ */
+void nix_c_context_free(nix_c_context * context);
+/**
+ *  @}
+ */
+
+/**
+ * @brief Initializes nix_libutil and its dependencies.
+ *
+ * This function can be called multiple times, but should be called at least
+ * once prior to any other nix function.
+ *
+ * @param[out] context Optional, stores error information
+ * @return NIX_OK if the initialization is successful, or an error code
+ * otherwise.
+ */
+nix_err nix_libutil_init(nix_c_context * context);
+
+/** @defgroup settings
+ *  @{
+ */
+/**
+ * @brief Retrieves a setting from the nix global configuration.
+ *
+ * This function requires nix_libutil_init() to be called at least once prior to
+ * its use.
+ *
+ * @param[out] context optional, Stores error information
+ * @param[in] key The key of the setting to retrieve.
+ * @param[in] callback Called with the setting value.
+ * @param[in] user_data optional, arbitrary data, passed to the callback when it's called.
+ * @see nix_get_string_callback
+ * @return NIX_ERR_KEY if the setting is unknown, or NIX_OK if the setting was retrieved
+ * successfully.
+ */
+nix_err nix_setting_get(nix_c_context * context, const char * key, nix_get_string_callback callback, void * user_data);
+
+/**
+ * @brief Sets a setting in the nix global configuration.
+ *
+ * Use "extra-<setting name>" to append to the setting's value.
+ *
+ * Settings only apply for new State%s. Call nix_plugins_init() when you are
+ * done with the settings to load any plugins.
+ *
+ * @param[out] context optional, Stores error information
+ * @param[in] key The key of the setting to set.
+ * @param[in] value The value to set for the setting.
+ * @return NIX_ERR_KEY if the setting is unknown, or NIX_OK if the setting was
+ * set successfully.
+ */
+nix_err nix_setting_set(nix_c_context * context, const char * key, const char * value);
+
+/**
+ *  @}
+ */
+// todo: nix_plugins_init()
+
+/**
+ * @brief Retrieves the nix library version.
+ *
+ * Does not fail.
+ * @return A static string representing the version of the nix library.
+ */
+const char * nix_version_get();
+
+/** @addtogroup errors
+ *  @{
+ */
+/**
+ * @brief Retrieves the most recent error message from a context.
+ *
+ * @pre This function should only be called after a previous nix function has
+ * returned an error.
+ *
+ * @param[out] context optional, the context to store errors in if this function
+ * fails
+ * @param[in] ctx the context to retrieve the error message from
+ * @param[out] n optional: a pointer to an unsigned int that is set to the
+ * length of the error.
+ * @return nullptr if no error message was ever set,
+ *         a borrowed pointer to the error message otherwise, which is valid
+ *         until the next call to a Nix function, or until the context is
+ *         destroyed.
+ */
+const char * nix_err_msg(nix_c_context * context, const nix_c_context * ctx, unsigned int * n);
+
+/**
+ * @brief Retrieves the error message from errorInfo in a context.
+ *
+ * Used to inspect nix Error messages.
+ *
+ * @pre This function should only be called after a previous nix function has
+ * returned a NIX_ERR_NIX_ERROR
+ *
+ * @param[out] context optional, the context to store errors in if this function
+ * fails
+ * @param[in] read_context the context to retrieve the error message from.
+ * @param[in] callback Called with the error message.
+ * @param[in] user_data optional, arbitrary data, passed to the callback when it's called.
+ * @see nix_get_string_callback
+ * @return NIX_OK if there were no errors, an error code otherwise.
+ */
+nix_err nix_err_info_msg(
+    nix_c_context * context, const nix_c_context * read_context, nix_get_string_callback callback, void * user_data);
+
+/**
+ * @brief Retrieves the error name from a context.
+ *
+ * Used to inspect nix Error messages.
+ *
+ * @pre This function should only be called after a previous nix function has
+ * returned a NIX_ERR_NIX_ERROR
+ *
+ * @param context optional, the context to store errors in if this function
+ * fails
+ * @param[in] read_context the context to retrieve the error message from
+ * @param[in] callback Called with the error name.
+ * @param[in] user_data optional, arbitrary data, passed to the callback when it's called.
+ * @see nix_get_string_callback
+ * @return NIX_OK if there were no errors, an error code otherwise.
+ */
+nix_err nix_err_name(
+    nix_c_context * context, const nix_c_context * read_context, nix_get_string_callback callback, void * user_data);
+
+/**
+ * @brief Retrieves the most recent error code from a nix_c_context
+ *
+ * Equivalent to reading the first field of the context.
+ *
+ * Does not fail
+ *
+ * @param[in] read_context the context to retrieve the error message from
+ * @return most recent error code stored in the context.
+ */
+nix_err nix_err_code(const nix_c_context * read_context);
+
+/**
+ * @brief Set an error message on a nix context.
+ *
+ * This should be used when you want to throw an error from a PrimOp callback.
+ *
+ * All other use is internal to the API.
+ *
+ * @param context context to write the error message to, required unless C++ exceptions are supported
+ * @param err The error code to set and return
+ * @param msg The error message to set. This string is copied.
+ * @returns the error code set
+ */
+nix_err nix_set_err_msg(nix_c_context * context, nix_err err, const char * msg);
+
+/**
+ * @brief Clear the error message from a nix context.
+ *
+ * This is performed implicitly by all functions that accept a context, so
+ * this won't be necessary in most cases.
+ * However, if you want to clear the error message without calling another
+ * function, you can use this.
+ *
+ * Example use case: a higher order function that helps with error handling,
+ * to make it more robust in the following scenario:
+ *
+ * 1. A previous call failed, and the error was caught and handled.
+ * 2. The context is reused with our error handling helper function.
+ * 3. The callback passed to the helper function doesn't actually make a call to
+ *    a Nix function.
+ * 4. The handled error is raised again, from an unrelated call.
+ *
+ * This failure can be avoided by clearing the error message after handling it.
+ */
+void nix_clear_err(nix_c_context * context);
+
+/**
+ *  @}
+ */
+
+// cffi end
+#ifdef __cplusplus
+}
+#endif
+
+/** @} */
+#endif // NIX_API_UTIL_H

subprojects/libutil-c/nix_api_util_internal.h

@@ -0,0 +1,50 @@
+#ifndef NIX_API_UTIL_INTERNAL_H
+#define NIX_API_UTIL_INTERNAL_H
+
+#include <string>
+#include <optional>
+
+#include "error.hh"
+#include "nix_api_util.h"
+
+struct nix_c_context
+{
+    nix_err last_err_code = NIX_OK;
+    /** The last error message. Always check last_err_code. This may not have been cleared, so that clearing is fast. */
+    std::optional<std::string> last_err = {};
+    std::optional<nix::ErrorInfo> info = {};
+    std::string name = "";
+};
+
+nix_err nix_context_error(nix_c_context * context);
+
+/**
+ * Internal use only.
+ *
+ * Helper to invoke nix_get_string_callback
+ * @param context optional, the context to store errors in if this function
+ * fails
+ * @param str The string to observe
+ * @param callback Called with the observed string.
+ * @param user_data optional, arbitrary data, passed to the callback when it's called.
+ * @return NIX_OK if there were no errors.
+ * @see nix_get_string_callback
+ */
+nix_err call_nix_get_string_callback(const std::string str, nix_get_string_callback callback, void * user_data);
+
+#define NIXC_CATCH_ERRS \
+    catch (...) \
+    { \
+        return nix_context_error(context); \
+    } \
+    return NIX_OK;
+
+#define NIXC_CATCH_ERRS_RES(def) \
+    catch (...) \
+    { \
+        nix_context_error(context); \
+        return def; \
+    }
+#define NIXC_CATCH_ERRS_NULL NIXC_CATCH_ERRS_RES(nullptr)
+
+#endif // NIX_API_UTIL_INTERNAL_H

subprojects/libutil-c/package.nix

@@ -0,0 +1,73 @@
+{ lib
+, stdenv
+, mkMesonDerivation
+, releaseTools
+
+, meson
+, ninja
+, pkg-config
+
+, nix-util
+
+# Configuration Options
+
+, version
+}:
+
+let
+  inherit (lib) fileset;
+in
+
+mkMesonDerivation (finalAttrs: {
+  pname = "nix-util-c";
+  inherit version;
+
+  workDir = ./.;
+  fileset = fileset.unions [
+    ../../build-utils-meson
+    ./build-utils-meson
+    ../../.version
+    ./.version
+    ./meson.build
+    ./meson.options
+    (fileset.fileFilter (file: file.hasExt "cc") ./.)
+    (fileset.fileFilter (file: file.hasExt "hh") ./.)
+    (fileset.fileFilter (file: file.hasExt "h") ./.)
+  ];
+
+  outputs = [ "out" "dev" ];
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+  ];
+
+  propagatedBuildInputs = [
+    nix-util
+  ];
+
+  preConfigure =
+    # "Inline" .version so it's not a symlink, and includes the suffix.
+    # Do the meson utils, without modification.
+    ''
+      chmod u+w ./.version
+      echo ${version} > ../../.version
+    '';
+
+  mesonFlags = [
+  ];
+
+  env = lib.optionalAttrs (stdenv.isLinux && !(stdenv.hostPlatform.isStatic && stdenv.system == "aarch64-linux")) {
+    LDFLAGS = "-fuse-ld=gold";
+  };
+
+  separateDebugInfo = !stdenv.hostPlatform.isStatic;
+
+  hardeningDisable = lib.optional stdenv.hostPlatform.isStatic "pie";
+
+  meta = {
+    platforms = lib.platforms.unix ++ lib.platforms.windows;
+  };
+
+})