Solo-C: a tiny coding agent in a single C file

main.c is the whole agent: a readline REPL that talks to any OpenAI-compatible
/chat/completions endpoint and exposes exactly one tool, bash(command). Commands
run through the user's shell with stdout and stderr merged, a hard timeout, and
a process-group kill; the output and an exit marker go back to the model until
it answers without calling a tool.

make static-deps builds curl and c-ares from source into static-deps/, so
`make static` can link a fully static binary on distros that get in the way: the
distro libcurl.a drags in libpsl, brotli, zstd and nghttp2, whose static objects
are GCC 14 LTO bytecode a newer linker cannot read, and a minimal system often
ships no libcares.a at all.

Two details worth keeping in mind when editing mkstaticdeps.sh. curl 8.22 takes
--enable-ares=PREFIX rather than the older --with-cares, and it only warns
about options it does not recognise, so the wrong spelling turns off async DNS
in silence instead of failing. And link order is load-bearing: libcares.a has
to come after libcurl.a or ares_* stays undefined.

Makefile

@@ -0,0 +1,61 @@
+CC = gcc
+CFLAGS = -Wall -Wextra -O2 -std=c99 -march=native $(shell pkg-config --cflags libcurl json-c readline)
+LDLIBS = $(shell pkg-config --libs libcurl json-c readline)
+
+# Fully static binary.
+#
+# The distro libcurl.a cannot be linked statically on Alpine: it pulls in
+# libpsl, libbrotli, libzstd and libnghttp2, whose static archives hold LTO
+# bytecode from GCC 14 that the installed GCC 15 cannot read ("bytecode
+# stream ... generated with LTO version 14.0 instead of the expected 15.1"),
+# so psl_*/Brotli*/ZSTD* never resolve. -fno-lto does not help; the objects
+# are bytecode, not C.
+#
+# static-deps/libcurl.a is curl built without those four libraries, leaving
+# only LTO-free static deps. Regenerate with: make static-deps
+#
+# c-ares is built from source by the same script, for two reasons: a minimal
+# system often has no libcares.a at all (Void's c-ares-devel ships the shared
+# library only), and where an archive does exist it can carry the same LTO
+# bytecode as the distro libcurl.a. Building it also pins the version.
+#
+# Archive order matters: libcurl.a pulls in ares_* symbols, so libcares.a has to
+# come after it on the link line.
+CURL_STATIC ?= static-deps/libcurl.a
+CARES_STATIC ?= static-deps/libcares.a
+STATIC_LIBS = $(CURL_STATIC) $(CARES_STATIC) -lssl -lcrypto -lz -lidn2 -lunistring \
+	-lreadline -lncursesw -ljson-c -lm -ldl -pthread
+
+solo: main.c
+	$(CC) $(CFLAGS) -o solo main.c $(LDLIBS)
+	strip solo
+
+static: main.c
+	@for f in $(CURL_STATIC) $(CARES_STATIC); do \
+		test -f $$f || { echo "missing $$f - run: make static-deps"; exit 1; }; \
+	done
+	$(CC) $(CFLAGS) -fno-lto -static -o solo-static main.c $(STATIC_LIBS)
+	strip solo-static
+
+static-deps:
+	sh ./mkstaticdeps.sh
+
+# Rebuild both archives from scratch, ignoring what is already there.
+static-deps-force:
+	FORCE=1 sh ./mkstaticdeps.sh
+
+PREFIX ?= /usr/local
+BINDIR = $(PREFIX)/bin
+INSTALL ?= install
+
+install: solo
+	$(INSTALL) -d $(DESTDIR)$(BINDIR)
+	$(INSTALL) -m 755 solo $(DESTDIR)$(BINDIR)/solo
+
+uninstall:
+	rm -f $(DESTDIR)$(BINDIR)/solo $(DESTDIR)$(BINDIR)/solo-static
+
+clean:
+	rm -f solo solo-static
+
+.PHONY: clean static static-deps static-deps-force install uninstall