Move /src to /subprojects

This will facilitate breaking up Nix into multiple packages for each
component with Meson.

subprojects/libmain/shared.hh

@@ -0,0 +1,147 @@
+#pragma once
+///@file
+
+#include "file-descriptor.hh"
+#include "processes.hh"
+#include "args.hh"
+#include "args/root.hh"
+#include "common-args.hh"
+#include "path.hh"
+#include "derived-path.hh"
+
+#include <signal.h>
+
+namespace nix {
+
+int handleExceptions(const std::string & programName, std::function<void()> fun);
+
+/**
+ * Don't forget to call initPlugins() after settings are initialized!
+ * @param loadConfig Whether to load configuration from `nix.conf`, `NIX_CONFIG`, etc. May be disabled for unit tests.
+ */
+void initNix(bool loadConfig = true);
+
+void parseCmdLine(int argc, char * * argv,
+    std::function<bool(Strings::iterator & arg, const Strings::iterator & end)> parseArg);
+
+void parseCmdLine(const std::string & programName, const Strings & args,
+    std::function<bool(Strings::iterator & arg, const Strings::iterator & end)> parseArg);
+
+void printVersion(const std::string & programName);
+
+/**
+ * Ugh.  No better place to put this.
+ */
+void printGCWarning();
+
+class Store;
+
+void printMissing(
+    ref<Store> store,
+    const std::vector<DerivedPath> & paths,
+    Verbosity lvl = lvlInfo);
+
+void printMissing(ref<Store> store, const StorePathSet & willBuild,
+    const StorePathSet & willSubstitute, const StorePathSet & unknown,
+    uint64_t downloadSize, uint64_t narSize, Verbosity lvl = lvlInfo);
+
+std::string getArg(const std::string & opt,
+    Strings::iterator & i, const Strings::iterator & end);
+
+template<class N> N getIntArg(const std::string & opt,
+    Strings::iterator & i, const Strings::iterator & end, bool allowUnit)
+{
+    ++i;
+    if (i == end) throw UsageError("'%1%' requires an argument", opt);
+    return string2IntWithUnitPrefix<N>(*i);
+}
+
+
+struct LegacyArgs : public MixCommonArgs, public RootArgs
+{
+    std::function<bool(Strings::iterator & arg, const Strings::iterator & end)> parseArg;
+
+    LegacyArgs(const std::string & programName,
+        std::function<bool(Strings::iterator & arg, const Strings::iterator & end)> parseArg);
+
+    bool processFlag(Strings::iterator & pos, Strings::iterator end) override;
+
+    bool processArgs(const Strings & args, bool finish) override;
+};
+
+
+/**
+ * Show the manual page for the specified program.
+ */
+void showManPage(const std::string & name);
+
+/**
+ * The constructor of this class starts a pager if standard output is a
+ * terminal and $PAGER is set. Standard output is redirected to the
+ * pager.
+ */
+class RunPager
+{
+public:
+    RunPager();
+    ~RunPager();
+
+private:
+#ifndef _WIN32 // TODO re-enable on Windows, once we can start processes.
+    Pid pid;
+#endif
+    Descriptor std_out;
+};
+
+extern volatile ::sig_atomic_t blockInt;
+
+
+/* GC helpers. */
+
+std::string showBytes(uint64_t bytes);
+
+struct GCResults;
+
+struct PrintFreed
+{
+    bool show;
+    const GCResults & results;
+    PrintFreed(bool show, const GCResults & results)
+        : show(show), results(results) { }
+    ~PrintFreed();
+};
+
+
+#ifndef _WIN32
+/**
+ * Install a SIGSEGV handler to detect stack overflows.
+ */
+void detectStackOverflow();
+
+/**
+ * Pluggable behavior to run in case of a stack overflow.
+ *
+ * Default value: defaultStackOverflowHandler.
+ *
+ * This is called by the handler installed by detectStackOverflow().
+ *
+ * This gives Nix library consumers a limit opportunity to report the error
+ * condition. The handler should exit the process.
+ * See defaultStackOverflowHandler() for a reference implementation.
+ *
+ * NOTE: Use with diligence, because this runs in the signal handler, with very
+ * limited stack space and a potentially a corrupted heap, all while the failed
+ * thread is blocked indefinitely. All functions called must be reentrant.
+ */
+extern std::function<void(siginfo_t * info, void * ctx)> stackOverflowHandler;
+
+/**
+ * The default, robust implementation of stackOverflowHandler.
+ *
+ * Prints an error message directly to stderr using a syscall instead of the
+ * logger. Exits the process immediately after.
+ */
+void defaultStackOverflowHandler(siginfo_t * info, void * ctx);
+#endif
+
+}