On 8/21/25 1:01 AM, John Ericson wrote:
A follow-up from "driver: Rework for_each_path using C++"These types are, for all intents and purposes, single-use closure environment types. It is much more ergonomic to juse use lambdas for this. On IRC there was concern about static dispatch and compile times with lambdas, but I have kept the class hierarchy and virtual methods from the previous commit that keeps `find_within_paths::for_each_path` untemplated, and I believe that add addresses the issue. Note that `struct spec_path` was *not* converted because it is used multiple times. We could stil convert to a lambda, but we would want to put the for_each_path call with that lambda inside a separate function anyways, to support the multiple callers. Unlike the other two refactors, it is not clear that this one would make anything shorter. gcc/ChangeLog: * gcc.cc (struct add_to_obstack): Gone, lambda capture list replaces it. (struct file_at_path): Gone, lambda capture list replaces it. (add_to_obstack::callback): Moved to lambda in build_search_list. (file_at_path::callback): Moved to lambda in fine_a_file. (for_each_path): New tiny templated wrapper for lambda (build_search_list): Use for_each_path with lambda. (find_a_file): Use for_each_path with lambda. Signed-off-by: John Ericson <g...@johnericson.me> --- gcc/gcc.cc | 142 +++++++++++++++++++++++++---------------------------- 1 file changed, 66 insertions(+), 76 deletions(-) diff --git a/gcc/gcc.cc b/gcc/gcc.cc index d43a347d120..94d9f760da6 100644 --- a/gcc/gcc.cc +++ b/gcc/gcc.cc @@ -2944,30 +2944,28 @@ find_within_paths::for_each_path (const struct path_prefix *paths, return ret; }-/* Callback for build_search_list. Adds path to obstack being built. */- -struct add_to_obstack : find_within_paths { - struct obstack *ob; - bool check_dir; - bool first_time; - -private: - void *callback (char *path) override; -}; - -void * -add_to_obstack::callback (char *path) +/* This is an adapter for using a lambda. It is separate from + find_within_paths::for_each_path in order that the main body of the + function (that function) *not* be template-specialised, and just this + tiny wrapper is instead. */ +template<typename fun> +static void * +for_each_path (const struct path_prefix *paths, + bool do_multi, + size_t extra_space, + fun && callback) { - if (check_dir && !is_directory (path)) - return NULL; - - if (!first_time) - obstack_1grow (ob, PATH_SEPARATOR); - - obstack_grow (ob, path, strlen (path)); - - first_time = false; - return NULL; + struct adapter : find_within_paths { + fun cb; + adapter(fun && cb) : cb{cb} {} + private: + void *callback (char *path) override + { + return cb(path); + } + }; + adapter a{std::move(callback)}; + return a.for_each_path(paths, do_multi, extra_space); }/* Add or change the value of an environment variable, outputting the@@ -2990,16 +2988,25 @@ static char * build_search_list (const struct path_prefix *paths, const char *prefix, bool check_dir, bool do_multi) { - struct add_to_obstack info; - - info.ob = &collect_obstack; - info.check_dir = check_dir; - info.first_time = true; + struct obstack *const ob = &collect_obstack; + bool first_time = true;obstack_grow (&collect_obstack, prefix, strlen (prefix));obstack_1grow (&collect_obstack, '=');- info.for_each_path (paths, do_multi, 0);+ /* Callback adds path to obstack being built. */ + for_each_path (paths, do_multi, 0, [ob, &first_time, check_dir](char *path) -> void* {
Line too long; the simplest fix would be to simplify the capture list to [&]. Also, the { should be on the next line, per
https://gcc.gnu.org/codingconventions.html#Lambda_Form
@@ -3093,14 +3060,37 @@ find_a_file (const struct path_prefix *pprefix, const char *name, int mode, return NULL; }- info.name = name;- info.suffix = (mode & X_OK) != 0 ? HOST_EXECUTABLE_SUFFIX : ""; - info.name_len = strlen (info.name); - info.suffix_len = strlen (info.suffix); - info.mode = mode; + const char *suffix = (mode & X_OK) != 0 ? HOST_EXECUTABLE_SUFFIX : ""; + const int name_len = strlen (name); + const int suffix_len = strlen (suffix); + + + /* Callback appends the file name to the directory path. If the + resulting file exists in the right mode, return the full pathname + to the file. */ + return (char*) for_each_path (pprefix, do_multi, + name_len + suffix_len, + [name, suffix, suffix_len, name_len, mode](char *path) -> void* {
Likewise. Or optionally [=] in this case. Jason
