Move /src to /subprojects

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

subprojects/libutil/current-process.cc

@@ -0,0 +1,152 @@
+#include <algorithm>
+#include <cstring>
+
+#include "current-process.hh"
+#include "util.hh"
+#include "finally.hh"
+#include "file-system.hh"
+#include "processes.hh"
+#include "signals.hh"
+#include <math.h>
+
+#ifdef __APPLE__
+# include <mach-o/dyld.h>
+#endif
+
+#if __linux__
+# include <mutex>
+# include "cgroup.hh"
+# include "namespaces.hh"
+#endif
+
+#ifndef _WIN32
+# include <sys/resource.h>
+#endif
+
+namespace nix {
+
+unsigned int getMaxCPU()
+{
+    #if __linux__
+    try {
+        auto cgroupFS = getCgroupFS();
+        if (!cgroupFS) return 0;
+
+        auto cpuFile = *cgroupFS + "/" + getCurrentCgroup() + "/cpu.max";
+
+        auto cpuMax = readFile(cpuFile);
+        auto cpuMaxParts = tokenizeString<std::vector<std::string>>(cpuMax, " \n");
+
+        if (cpuMaxParts.size() != 2) {
+            return 0;
+        }
+
+        auto quota = cpuMaxParts[0];
+        auto period = cpuMaxParts[1];
+        if (quota != "max")
+                return std::ceil(std::stoi(quota) / std::stof(period));
+    } catch (Error &) { ignoreExceptionInDestructor(lvlDebug); }
+    #endif
+
+    return 0;
+}
+
+
+//////////////////////////////////////////////////////////////////////
+
+
+size_t savedStackSize = 0;
+
+void setStackSize(size_t stackSize)
+{
+    #ifndef _WIN32
+    struct rlimit limit;
+    if (getrlimit(RLIMIT_STACK, &limit) == 0 && limit.rlim_cur < stackSize) {
+        savedStackSize = limit.rlim_cur;
+        limit.rlim_cur = std::min(static_cast<rlim_t>(stackSize), limit.rlim_max);
+        if (setrlimit(RLIMIT_STACK, &limit) != 0) {
+            logger->log(
+                lvlError,
+                HintFmt(
+                    "Failed to increase stack size from %1% to %2% (maximum allowed stack size: %3%): %4%",
+                    savedStackSize,
+                    stackSize,
+                    limit.rlim_max,
+                    std::strerror(errno)
+                ).str()
+            );
+        }
+    }
+    #else
+    ULONG_PTR stackLow, stackHigh;
+    GetCurrentThreadStackLimits(&stackLow, &stackHigh);
+    ULONG maxStackSize = stackHigh - stackLow;
+    ULONG currStackSize = 0;
+    // This retrieves the current promised stack size
+    SetThreadStackGuarantee(&currStackSize);
+    if (currStackSize < stackSize) {
+        savedStackSize = currStackSize;
+        ULONG newStackSize = std::min(static_cast<ULONG>(stackSize), maxStackSize);
+        if (SetThreadStackGuarantee(&newStackSize) == 0) {
+            logger->log(
+                lvlError,
+                HintFmt(
+                    "Failed to increase stack size from %1% to %2% (maximum allowed stack size: %3%): %4%",
+                    savedStackSize,
+                    stackSize,
+                    maxStackSize,
+                    std::to_string(GetLastError())
+                ).str()
+            );
+        }
+    }
+    #endif
+}
+
+void restoreProcessContext(bool restoreMounts)
+{
+    #ifndef _WIN32
+    unix::restoreSignals();
+    #endif
+    if (restoreMounts) {
+        #if __linux__
+        restoreMountNamespace();
+        #endif
+    }
+
+    #ifndef _WIN32
+    if (savedStackSize) {
+        struct rlimit limit;
+        if (getrlimit(RLIMIT_STACK, &limit) == 0) {
+            limit.rlim_cur = savedStackSize;
+            setrlimit(RLIMIT_STACK, &limit);
+        }
+    }
+    #endif
+}
+
+
+//////////////////////////////////////////////////////////////////////
+
+
+std::optional<Path> getSelfExe()
+{
+    static auto cached = []() -> std::optional<Path>
+    {
+        #if __linux__ || __GNU__
+        return readLink("/proc/self/exe");
+        #elif __APPLE__
+        char buf[1024];
+        uint32_t size = sizeof(buf);
+        if (_NSGetExecutablePath(buf, &size) == 0)
+            return buf;
+        else
+            return std::nullopt;
+        #else
+        return std::nullopt;
+        #endif
+    }();
+    return cached;
+}
+
+}