gccNGPackages: Rework threading model patch based on feedback on IRC (#424918)

pkgs/development/compilers/gcc/ng/15/gcc/custom-threading-model.patch

@@ -1,59 +1,50 @@
-From 1eaf7ce77bb4eb73e5565ede220557c2ef0290b0 Mon Sep 17 00:00:00 2001
+From 46280d27a5c96b2efa7a61f49ee8dc14f7e10d0c Mon Sep 17 00:00:00 2001
 From: John Ericson <git@JohnEricson.me>
 Date: Sun, 22 Aug 2021 01:14:22 -0400
-Subject: [PATCH] Allow explicitly specifying the thread model for runtime libs
+Subject: [PATCH] Factor out thread model detection with `GCC_AC_THREAD_MODEL`
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
 
-Previously, they always scraped the thread mode from `$CC -v', now, that
+This macro deduplicates the
-is the default but one may pass `--with-threads=MODEL` to be explicit
-instead.
 
-One use-case is bootstraping with a shorter critical path. The
+    $CC -v 2>&1 | sed -n 's/^Thread model: //p'
-traditionally route was to build an entire "static stage" GCC, build
-libc, and then build GCC again supporting dynamic linking,
-multithreading, etc. But this is wasteful in that GCC itself is built
-twice.
 
-With this change, rather than having to mess with spec files we can just
+check that was occurring in various runtime libs.
-configure the runtime libraries the way we want directly. In turn, that
-opens to just building libgcc twice rather than all of GCC.
 
-Frankly, specs were always a rather indirect approach to coordinate this
+Additionally, as a bit of an Easter egg, this also allows overriding
-during GCC's bootstrap, since GCC itself really doesn't care what the
+what the compiler would return by setting the
-threading model is, just that the runtime libraries agree among
+`gcc_cv_target_thread_file` cache variable first. I admit that it is in
-themselves. Relying on a hard-coded spec for this also keeps us one step
+fact this Easter egg that led me to write the patch. The use-case for it
-further from the long-term goal of multi-target GCC, for what it's
+is for making multilib builds where the library sets do not all share
-worth.
+the same thread model easier. See also `THREAD_MODEL_SPEC` for more
+about the varying thread models use-case.
 
-For the record, "single stage" builds of GCC have some precedent in
+Arguably one could could try to define on `THREAD_MODEL_SPEC` on more
-downstream packaging, for example with [1]. That one, as far as I can
+platforms (besides e.g. AIX) but the ramifications of this are a bit
-tell, builds libgcc once, but with the headers of the libc
+unclear. Setting `gcc_cv_target_thread_file` directly is a "low tech"
-implementation provided and then cyclic linking down later. They are
+solution that will work for now for sure. Of course, since setting a
-both fine approaches, but I don't think one should have to be forced
+cache variable like this a hacky trick, I will not expect this to be at
-into cyclic dependencies if they don't want to. That opens the door to
+all stable/guaranteed to work, going forward.
-non-terminating programs due to, e.g., atomics used in a threads
-implementation being lowered to threads absent hardware support.
 
-Finally, I understand that such custom bootstrapping is not officially
+Thanks to Arsen who on IRC discussed these things with me, including in
-supported. I don't mean to imply it should be --- a lot more cleanup
+particular making it a cache var not `--with-model` flag, to not
-work to the build system would be necessary before supporting it
+prematurely foster expectations that this is stable.
-wouldn't be a huge additional maintainer burden --- I just hope to add a
-reasonable knob for those comfortable with doing unsupported things
-already.
 
-[1]: https://github.com/richfelker/musl-cross-make
+Suggested-by: Arsen Arsenović <arsen@aarsen.me>
 ---
- config/gthr.m4              | 32 ++++++++++++++++++++++++++++++++
+ config/gthr.m4              | 23 +++++++++++++++++++++++
  libatomic/configure.ac      |  4 +---
  libgcc/configure.ac         |  4 +---
  libphobos/m4/druntime/os.m4 |  2 +-
  libstdc++-v3/acinclude.m4   |  8 +++-----
- 5 files changed, 38 insertions(+), 12 deletions(-)
+ 5 files changed, 29 insertions(+), 12 deletions(-)
 
 diff --git a/config/gthr.m4 b/config/gthr.m4
-index 11996247f15..7aed5d3df0d 100644
+index 11996247f15..e8fac4a5721 100644
 --- a/config/gthr.m4
 +++ b/config/gthr.m4
-@@ -5,6 +5,35 @@ dnl Public License, this file may be distributed as part of a program
+@@ -5,6 +5,26 @@ dnl Public License, this file may be distributed as part of a program
  dnl that contains a configuration script generated by Autoconf, under
  dnl the same distribution terms as the rest of that program.
  
@@ -62,34 +53,25 @@ index 11996247f15..7aed5d3df0d 100644
 +dnl usage: GCC_AC_THREAD_MODEL
 +AC_DEFUN([GCC_AC_THREAD_MODEL],
 +[
-+# With threads
++# Specify the threading model for this GCC runtime library
 +# Pass with no value to take from compiler's metadata
 +# Pass with a value to specify a thread package
 +# 'single' means single threaded -- without threads.
-+AC_ARG_WITH(threads,
++AC_CACHE_CHECK([for the threading model used by GCC], [gcc_cv_target_thread_file], [
-+[AS_HELP_STRING([[--with-threads=MODEL]],
++  # Set new cache variable
-+		[specify thread model for this GCC
++  gcc_cv_target_thread_file=`$CC -v 2>&1 | sed -n 's/^Thread model: //p'`
-+		 runtime library])],,
++])
-+[with_threads=''])
++# Set variable name (not prefixed enough to be a good cache variable
-+
++# name) traditionally used for this purpose, to avoid having to change
-+if test x"$with_threads" = x'yes'; then
++# a bunch of configure scripts.
-+    AC_MSG_ERROR([Cannot pass bare --with-threads, must pass explicit --with-threads=MODEL])
++target_thread_file="$gcc_cv_target_thread_file"
-+elif test x"$with_threads" = x'no'; then
-+    target_thread_file=single
-+elif test x"$with_threads" = x''; then
-+    AC_MSG_CHECKING([for thread model used by GCC])
-+    target_thread_file=`$CC -v 2>&1 | sed -n 's/^Thread model: //p'`
-+    AC_MSG_RESULT([$target_thread_file])
-+else
-+    target_thread_file=$with_threads
-+fi
 +])
 +
 +
  dnl Define header location by thread model
  
  dnl usage: GCC_AC_THREAD_HEADER([thread_model])
-@@ -23,6 +52,9 @@ case $1 in
+@@ -23,6 +43,9 @@ case $1 in
      vxworks)	thread_header=config/gthr-vxworks.h ;;
      win32)	thread_header=config/i386/gthr-win32.h ;;
      mcf)	thread_header=config/i386/gthr-mcf.h ;;
@@ -100,7 +82,7 @@ index 11996247f15..7aed5d3df0d 100644
  AC_SUBST(thread_header)
  ])
 diff --git a/libatomic/configure.ac b/libatomic/configure.ac
-index 85824fa7614..691f4948f6c 100644
+index aafae71028d..a1aa3bdf69f 100644
 --- a/libatomic/configure.ac
 +++ b/libatomic/configure.ac
 @@ -162,9 +162,7 @@ libtool_VERSION=3:0:2
@@ -115,7 +97,7 @@ index 85824fa7614..691f4948f6c 100644
  case "$target" in
   *aarch64*)
 diff --git a/libgcc/configure.ac b/libgcc/configure.ac
-index 4e8c036990f..acf54e24c79 100644
+index 85e4f1bc48b..d44493f9653 100644
 --- a/libgcc/configure.ac
 +++ b/libgcc/configure.ac
 @@ -305,9 +305,7 @@ AC_SUBST([use_tm_clone_registry])
@@ -130,7 +112,7 @@ index 4e8c036990f..acf54e24c79 100644
  # Check for assembler CFI support.
  AC_CACHE_CHECK([whether assembler supports CFI directives], [libgcc_cv_cfi],
 diff --git a/libphobos/m4/druntime/os.m4 b/libphobos/m4/druntime/os.m4
-index 15cde3b04b8..28bd4d3d2bd 100644
+index ef8ca434407..7bb91362dbe 100644
 --- a/libphobos/m4/druntime/os.m4
 +++ b/libphobos/m4/druntime/os.m4
 @@ -32,7 +32,7 @@ case $1 in
@@ -143,10 +125,10 @@ index 15cde3b04b8..28bd4d3d2bd 100644
  AC_SUBST(DCFG_THREAD_MODEL)
  ])
 diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
-index 51a08bcc8b1..71697f59d6d 100644
+index a0094c2dd95..66fc3abe4fd 100644
 --- a/libstdc++-v3/acinclude.m4
 +++ b/libstdc++-v3/acinclude.m4
-@@ -4342,9 +4342,7 @@ dnl Substs:
+@@ -4345,9 +4345,7 @@ dnl Substs:
  dnl  thread_header
  dnl
  AC_DEFUN([GLIBCXX_ENABLE_THREADS], [
@@ -157,7 +139,7 @@ index 51a08bcc8b1..71697f59d6d 100644
    GCC_AC_THREAD_HEADER([$target_thread_file])
  ])
  
-@@ -4354,7 +4352,8 @@ dnl Check if gthread implementation defines the types and functions
+@@ -4357,7 +4355,8 @@ dnl Check if gthread implementation defines the types and functions
  dnl required by the c++0x thread library.  Conforming gthread
  dnl implementations can define __GTHREADS_CXX0X to enable use with c++0x.
  dnl
@@ -167,7 +149,7 @@ index 51a08bcc8b1..71697f59d6d 100644
  dnl
  AC_DEFUN([GLIBCXX_CHECK_GTHREADS], [
    GLIBCXX_ENABLE(libstdcxx-threads,auto,,[enable C++11 threads support])
-@@ -4369,7 +4368,6 @@ AC_DEFUN([GLIBCXX_CHECK_GTHREADS], [
+@@ -4372,7 +4371,6 @@ AC_DEFUN([GLIBCXX_CHECK_GTHREADS], [
    CXXFLAGS="$CXXFLAGS -fno-exceptions \
  	-I${toplevel_srcdir}/libgcc -I${toplevel_builddir}/libgcc"
  
@@ -176,5 +158,5 @@ index 51a08bcc8b1..71697f59d6d 100644
      posix)
        CXXFLAGS="$CXXFLAGS -DSUPPORTS_WEAK -DGTHREAD_USE_WEAK -D_PTHREADS"
 -- 
-2.44.1
+2.47.2
 

pkgs/development/compilers/gcc/ng/common/gcc/default.nix

@@ -51,21 +51,10 @@ stdenv.mkDerivation (finalAttrs: {
   ];
 
   patches = [
-    # Submitted:
-    #  - https://gcc.gnu.org/pipermail/gcc-patches/2021-August/577639.html
-    #  - https://gcc.gnu.org/pipermail/gcc-patches/2021-August/577640.html
-    #  - https://gcc.gnu.org/pipermail/gcc-patches/2021-August/577638.html
-    #
-    # In Git: https://github.com/Ericson2314/gcc/tree/prog-target-15
     (getVersionFile "gcc/0001-find_a_program-First-search-with-machine-prefix.patch")
     (getVersionFile "gcc/0002-driver-for_each_pass-Pass-to-callback-whether-dir-is.patch")
     (getVersionFile "gcc/0003-find_a_program-Only-search-for-prefixed-paths-in-und.patch")
 
-    # Submitted: https://inbox.sourceware.org/gcc-patches/20210818203840.1550133-1-John.Ericson@Obsidian.Systems/T/#t
-    # In Git: https://github.com/Ericson2314/gcc/tree/libgcc-custom-threading-model-15
-    (getVersionFile "gcc/custom-threading-model.patch")
-
-    # TODO: fix up and send to upstream
     (getVersionFile "gcc/fix-collect2-paths.diff")
   ];
 

pkgs/development/compilers/gcc/ng/common/libgcc/default.nix

@@ -169,7 +169,7 @@ stdenv.mkDerivation (finalAttrs: {
 
   configureFlags = [
     "--disable-dependency-tracking"
-    "--with-threads=single"
+    "gcc_cv_target_thread_file=single"
     # $CC cannot link binaries, let alone run then
     "cross_compiling=true"
     # Do not have dynamic linker without libc

pkgs/development/compilers/gcc/ng/common/libgfortran/default.nix

@@ -158,7 +158,7 @@ stdenv.mkDerivation (finalAttrs: {
 
   configureFlags = [
     "--disable-dependency-tracking"
-    "--with-threads=single"
+    "gcc_cv_target_thread_file=single"
     # $CC cannot link binaries, let alone run then
     "cross_compiling=true"
   ];

pkgs/development/compilers/gcc/ng/common/libstdcxx/default.nix

@@ -53,7 +53,7 @@ stdenv.mkDerivation (finalAttrs: {
   configureFlags = [
     "--disable-dependency-tracking"
     "--with-toolexeclibdir=${builtins.placeholder "out"}/lib"
-    "--with-threads=posix"
+    "gcc_cv_target_thread_file=posix"
     "cross_compiling=true"
     "--disable-multilib"
 

pkgs/development/compilers/gcc/ng/common/patches.nix

@@ -1,10 +1,18 @@
 {
+  # TODO: fix up and send to upstream
   "gcc/fix-collect2-paths.diff" = [
     {
       after = "15";
       path = ../15;
     }
   ];
+
+  # Submitted (001--003):
+  #  - https://gcc.gnu.org/pipermail/gcc-patches/2021-August/577639.html
+  #  - https://gcc.gnu.org/pipermail/gcc-patches/2021-August/577640.html
+  #  - https://gcc.gnu.org/pipermail/gcc-patches/2021-August/577638.html
+  #
+  # In Git: https://github.com/Ericson2314/gcc/tree/prog-target-15
   "gcc/0001-find_a_program-First-search-with-machine-prefix.patch" = [
     {
       after = "15";
@@ -23,6 +31,9 @@
       path = ../15;
     }
   ];
+
+  # Submitted: https://gcc.gnu.org/pipermail/gcc-patches/2025-July/689429.html
+  # In Git: https://github.com/Ericson2314/gcc/tree/libgcc-custom-threading-model-15
   "gcc/custom-threading-model.patch" = [
     {
       after = "15";