Re: [PATCH v2 3/3] p1689r5: initial support
On Tue, Nov 01, 2022 at 08:57:37 -0600, Tom Tromey wrote: > > "Ben" == Ben Boeckel via Gcc-patches writes: > > Ben> - `-fdeps-file=` specifies the path to the file to write the format to. > > I don't know how this output is intended to be used, but one mistake > made with the other dependency-tracking options was that the output file > isn't created atomically. As a consequence, Makefiles normally have to > work around this to be robust. If that's a possible issue here then it > would be best to handle it in this patch. I don't think there'll be any race here because it's the "output" of the rule as far as the build graph is concerned. It's also JSON, so anything reading it "early" will get a partial object and easily detect "something went wrong". And for clarity, the `-o` flag used in CMake with this is just a side effect of the `-E` mechanism used and is completely ignored in the CMake usage of this. --Ben
Re: [PATCH v2 3/3] p1689r5: initial support
> "Ben" == Ben Boeckel via Gcc-patches writes: Ben> - `-fdeps-file=` specifies the path to the file to write the format to. I don't know how this output is intended to be used, but one mistake made with the other dependency-tracking options was that the output file isn't created atomically. As a consequence, Makefiles normally have to work around this to be robust. If that's a possible issue here then it would be best to handle it in this patch. Tom
Re: [PATCH v2 3/3] p1689r5: initial support
On Thu, Oct 27, 2022 at 19:16:44 -0400, Ben Boeckel wrote:
> diff --git a/gcc/testsuite/g++.dg/modules/modules.exp
> b/gcc/testsuite/g++.dg/modules/modules.exp
> index afb323d0efd..7fe8825144f 100644
> --- a/gcc/testsuite/g++.dg/modules/modules.exp
> +++ b/gcc/testsuite/g++.dg/modules/modules.exp
> @@ -28,6 +28,7 @@
> # { dg-module-do [link|run] [xfail] [options] } # link [and run]
>
> load_lib g++-dg.exp
> +load_lib modules.exp
>
> # If a testcase doesn't have special options, use these.
> global DEFAULT_CXXFLAGS
> @@ -237,6 +238,13 @@ proc cleanup_module_files { files } {
> }
> }
>
> +# delete the specified set of dep files
> +proc cleanup_dep_files { files } {
> +foreach file $files {
> + file_on_host delete $file
> +}
> +}
> +
> global testdir
> set testdir $srcdir/$subdir
> proc srcdir {} {
> @@ -310,6 +318,7 @@ foreach src [lsort [find $srcdir/$subdir {*_a.[CHX}]] {
> set std_list [module-init $src]
> foreach std $std_list {
> set mod_files {}
> + set dep_files {}
> global module_do
> set module_do {"compile" "P"}
> set asm_list {}
> @@ -346,6 +355,8 @@ foreach src [lsort [find $srcdir/$subdir {*_a.[CHX}]] {
> set mod_files [find $DEFAULT_REPO *.gcm]
> }
> cleanup_module_files $mod_files
> +
> + cleanup_dep_files $dep_files
> }
> }
> }
These `cleanup_dep_files` hunks are leftovers from my attempts at
getting the P1689 and flags tests working; they'll be gone in v3.
--Ben
[PATCH v2 3/3] p1689r5: initial support
This patch implements support for [P1689R5][] to communicate to a build system the C++20 module dependencies to build systems so that they may build `.gcm` files in the proper order. Support is communicated through the following three new flags: - `-fdeps-format=` specifies the format for the output. Currently named `p1689r5`. - `-fdeps-file=` specifies the path to the file to write the format to. - `-fdep-output=` specifies the `.o` that will be written for the TU that is scanned. This is required so that the build system can correlate the dependency output with the actual compilation that will occur. CMake supports this format as of 17 Jun 2022 (to be part of 3.25.0) using an experimental feature selection (to allow for future usage evolution without committing to how it works today). While it remains experimental, docs may be found in CMake's documentation for experimental features. Future work may include using this format for Fortran module dependencies as well, however this is still pending work. [P1689R5]: https://isocpp.org/files/papers/P1689R5.html [cmake-experimental]: https://gitlab.kitware.com/cmake/cmake/-/blob/master/Help/dev/experimental.rst TODO: - header-unit information fields Header units (including the standard library headers) are 100% unsupported right now because the `-E` mechanism wants to import their BMIs. A new mode (i.e., something more workable than existing `-E` behavior) that mocks up header units as if they were imported purely from their path and content would be required. - non-utf8 paths The current standard says that paths that are not unambiguously represented using UTF-8 are not supported (because these cases are rare and the extra complication is not worth it at this time). Future versions of the format might have ways of encoding non-UTF-8 paths. For now, this patch just doesn't support non-UTF-8 paths (ignoring the "unambiguously represetable in UTF-8" case). - figure out why junk gets placed at the end of the file Sometimes it seems like the file gets a lot of `NUL` bytes appended to it. It happens rarely and seems to be the result of some `ftruncate`-style call which results in extra padding in the contents. Noting it here as an observation at least. Signed-off-by: Ben Boeckel --- gcc/ChangeLog | 5 + gcc/c-family/ChangeLog| 6 + gcc/c-family/c-opts.cc| 40 +++- gcc/c-family/c.opt| 12 + gcc/cp/ChangeLog | 5 + gcc/cp/module.cc | 3 +- gcc/doc/invoke.texi | 15 ++ gcc/testsuite/ChangeLog | 7 + gcc/testsuite/g++.dg/modules/depflags-f-MD.C | 2 + gcc/testsuite/g++.dg/modules/depflags-f.C | 1 + gcc/testsuite/g++.dg/modules/depflags-fi.C| 3 + gcc/testsuite/g++.dg/modules/depflags-fj-MD.C | 3 + gcc/testsuite/g++.dg/modules/depflags-fj.C| 4 + .../g++.dg/modules/depflags-fjo-MD.C | 4 + gcc/testsuite/g++.dg/modules/depflags-fjo.C | 5 + gcc/testsuite/g++.dg/modules/depflags-fo-MD.C | 3 + gcc/testsuite/g++.dg/modules/depflags-fo.C| 4 + gcc/testsuite/g++.dg/modules/depflags-j-MD.C | 2 + gcc/testsuite/g++.dg/modules/depflags-j.C | 3 + gcc/testsuite/g++.dg/modules/depflags-jo-MD.C | 3 + gcc/testsuite/g++.dg/modules/depflags-jo.C| 4 + gcc/testsuite/g++.dg/modules/depflags-o-MD.C | 2 + gcc/testsuite/g++.dg/modules/depflags-o.C | 3 + gcc/testsuite/g++.dg/modules/modules.exp | 11 + gcc/testsuite/g++.dg/modules/p1689-1.C| 18 ++ gcc/testsuite/g++.dg/modules/p1689-1.exp.json | 27 +++ gcc/testsuite/g++.dg/modules/p1689-2.C| 16 ++ gcc/testsuite/g++.dg/modules/p1689-2.exp.json | 16 ++ gcc/testsuite/g++.dg/modules/p1689-3.C| 14 ++ gcc/testsuite/g++.dg/modules/p1689-3.exp.json | 16 ++ gcc/testsuite/g++.dg/modules/p1689-4.C| 14 ++ gcc/testsuite/g++.dg/modules/p1689-4.exp.json | 14 ++ gcc/testsuite/g++.dg/modules/p1689-5.C| 14 ++ gcc/testsuite/g++.dg/modules/p1689-5.exp.json | 14 ++ gcc/testsuite/g++.dg/modules/test-p1689.py| 222 ++ gcc/testsuite/lib/modules.exp | 71 ++ libcpp/ChangeLog | 11 + libcpp/include/cpplib.h | 12 +- libcpp/include/mkdeps.h | 17 +- libcpp/init.cc| 13 +- libcpp/mkdeps.cc | 149 +++- 41 files changed, 789 insertions(+), 19 deletions(-) create mode 100644 gcc/testsuite/g++.dg/modules/depflags-f-MD.C create mode 100644 gcc/testsuite/g++.dg/modules/depflags-f.C create mode 100644 gcc/testsuite/g++.dg/modules/depflags-fi.C create mode 100644 gcc/testsuite/g++.dg/modules/depflags-fj-MD.C create mode 100644 gcc/testsuite/g++.dg/modules/depflags-fj.C create mode 100644
