libstdc++-v3: some progress

README.md

@@ -32,7 +32,7 @@ First configure GCC as usual (follow `configure.sh`), but use a separate build f
 % export PREFIX="$(pwd)"
 % mkdir build-libstdc++
 % cd build-libstdc++
-% ../gcc-11.1.0/configure --prefix="$PREFIX" --target=sh3eb-elf --with-multilib-list=m3,m4-nofpu --enable-languages=c,c++ --without-headers --with-newlib --program-prefix=sh-elf- --enable-libssp --enable-lto --enable-clocale=generic --enable-libstdcxx-allocator --disable-threads --disable-hosted-libstdcxx --disable-libstdcxx-verbose
+% ../gcc-11.1.0/configure --prefix="$PREFIX" --target=sh3eb-elf --with-multilib-list=m3,m4-nofpu --enable-languages=c,c++ --without-headers --with-newlib --program-prefix=sh-elf- --enable-libssp --enable-lto --enable-clocale=generic --enable-libstdcxx-allocator --disable-threads --disable-hosted-libstdcxx --disable-libstdcxx-verbose --enable-cxx-flags="-ffreestanding"
 ```
 
 * `--enable-clocale=generic`: We want minimal locales and this is certainly the minimalistic option.
@@ -40,6 +40,7 @@ First configure GCC as usual (follow `configure.sh`), but use a separate build f
 * `--disable-threads`: Obvious.
 * `--disable-hosted-libstdcxx`: This builds only the free-standing subset of the library (one thing at a time).
 * `--disable-libstdcxx-verbose`: We don't have a systematic standard error stream anyway.
+* `--enable-cxx-flags="-ffreestanding"`: Really everything should be free-standing here. It doesn't apply to conftest programs apparently, which (fail to) link with the default C runtime (`crt1.o` etc), maybe something will need to be done about that in the future.
 
 Now build and install that GCC and the libgcc.
 
@@ -48,7 +49,16 @@ Now build and install that GCC and the libgcc.
 % make -j$(nproc) install-strip-gcc install-strip-target-libgcc
 ```
 
-Then go an install [fxlibc](https://gitea.planet-casio.com/Vhex-Kernel-Core/fxlibc/) since we're certainly not going to build the C++ standard library without the C standard library.
+Next step is to install [OpenLibm](https://gitea.planet-casio.com/Lephenixnoir/OpenLibm) and [fxlibc](https://gitea.planet-casio.com/Vhex-Kernel-Core/fxlibc/) since we're certainly not going to build the C++ standard library without the C standard library.
+
+For some reason OpenLibm installs its headers in the `include/openlibm` subfolder, but then includes them as if they were in `include`, so we have to add a path. Normally either the projet provides that path, or gint does it through its CMake find module. Here we can symlink to the `sh3eb-elf/sys-include` folder in this repo's root folder (or `include` but it's already symlinked to the compiler's install folder and we don't really want to override that).
+
+```
+% SRC="$(sh-elf-gcc -print-file-name=include/openlibm)"
+% DST="../sh3eb-elf/sys-include"
+% mkdir -p "$DST"
+% for x in "$SRC"/*.h; do ln -s "$x" "$DST/${x#$SRC/}"; done
+```
 
 After this, come back to the build folder, run the build command for libstdc++-v3, and hope it works out. I recommend not using `-j` as it makes error messages and logs more linear.
 
@@ -60,4 +70,12 @@ Since this will likely fail, check out `sh3eb-elf/libstdc++-v3/config.log` for c
 
 ### Current problems
 
-* The programs are built without `-ffreestanding`, which means anything autoconf tries to link is provided with GCC's C runtime in the form of `crt1.o` and other files we *really* don't want. There are some link errors due to missing symbols. The expected solution is to build everything with `-ffreestanding` (since it doesn't disable the libc, only `__STDC_HOSTED__` and this type of link mechanisms).
+Hard limits:
+
+* `<stdio.h>` is not complete yet.
+
+Suspected problems:
+
+* The conftest programs are built without `-ffreestanding`, which means autoconf cannot really link stuff. This is probably not too much of a problem, because it's cross-compiled anyway so there's nothing to do with a linked program, but who knows.
+
+* autoconf compiles conftest programs as if on a fully-featured dynamic OS, which is nowhere near true (eg. it builds with `-shared-libgcc`).