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feat: hosted libstdc++ for x86_64-montauk - full C++ on MontaukOS

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The cross toolchain now builds real hosted C++: std::string, vector,
unique_ptr, iostreams and exceptions all work in a plain
x86_64-montauk-g++ invocation with no special flags. This is the
library that native cc1plus will link against for the GCC self-host.

crt1 now runs .preinit_array/.init_array before main and hooks
.fini_array through atexit (main returns via exit(), so destructors
run on both exit paths). Global constructors and libgcc's eh_frame
registration both ride this. GCC is reconfigured with
--enable-initfini-array (modern arrays instead of .ctors),
--with-newlib (satisfies libstdc++'s crossconfig for unknown hosts),
--disable-wchar_t and --disable-libstdcxx-pch; the montauk gcc patch
grows a hunk keeping os/generic ctype under --with-newlib (the
Montauk libc is not newlib).

libc additions harvested by the libstdc++ build: mbtowc/wctomb,
strxfrm, strtok/strtok_r, a real vfscanf/fscanf/scanf (character-
driven with widths and l/ll; also unblocks gprof later), fgetpos/
fsetpos/setbuf/fpos_t, modf plus the C99 float math variants
(acosf..tanhf, hypot/hypotf as wrappers), FP_* classification macros,
the full POSIX errno vocabulary, complete DT_* dirent types, and
mbstate_t.

The SDK ships the real libstdc++.a (was an empty stand-in), the C++
headers at 0:/sdk/include/c++, and cxx-test.elf (global ctor, string,
vector+sort, unique_ptr, throw/catch; exits 0 on 5/5). Ramdisk sits
at 1571 files, within the 2048 table.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
daniel
2026-07-16 23:06:50 +02:00
co-authored by Claude Fable 5
parent eadc79708f
commit 03d1a1bc2f
19 changed files with 480 additions and 8 deletions
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programs/GNUmakefile
+3 -1
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@@ -401,8 +401,10 @@ ifneq ($(wildcard $(NATIVE_BIN)/as),)
cp lib/libc/liblibc.a $(BINDIR)/sdk/lib/libc.a
cp lib/libc/crt1.o lib/libc/crti.o lib/libc/crtn.o $(BINDIR)/sdk/lib/
ar rcs $(BINDIR)/sdk/lib/libm.a
ar rcs $(BINDIR)/sdk/lib/libstdc++.a
cp ../toolchain/local/x86_64-montauk/lib/libstdc++.a $(BINDIR)/sdk/lib/libstdc++.a
cp -r ../toolchain/local/x86_64-montauk/include/c++ $(BINDIR)/sdk/include/c++
../toolchain/local/bin/x86_64-montauk-gcc -O2 ../toolchain/files/tls-test.c -o $(BINDIR)/sdk/bin/tls-test.elf
../toolchain/local/bin/x86_64-montauk-g++ -O2 ../toolchain/files/cxx-test.cpp -o $(BINDIR)/sdk/bin/cxx-test.elf
else
@echo "devkit: toolchain/native/ not built; skipping native dev tools"
endif