test(libkernel): check that exits release the process session and the environment is validated

Run the process session in a test executable linked with libc and leave
through LibcExit and LibcExitWithoutHandlers: the backend is released once
in both. Check that a refused request is never released, that off never
reaches the backend, that a second session is refused, that an unset
APS5_GAME_MODE is accepted and that APS5_GAME_MODE=bogus is rejected with
an error naming the variable.

core/libs/tests/HostPerformanceProcess.cpp

@@ -0,0 +1,87 @@
+#include "prx/libc/include/Shutdown.hpp"
+#include "prx/libkernel/System/include/HostPerformance.hpp"
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <memory>
+#include <stdexcept>
+#include <string>
+
+namespace {
+
+using namespace HostPerformance;
+
+class PrintingBackend final : public IBackend {
+public:
+    explicit PrintingBackend(Outcome outcome) : outcome(outcome) {}
+    const char* Name() const override { return "printing"; }
+
+    BeginResult Begin() override {
+        std::puts("begin called");
+        return {outcome, "scripted"};
+    }
+
+    void End() override {
+        std::puts("release ran at exit");
+        std::fflush(stdout);
+    }
+
+private:
+    Outcome outcome;
+};
+
+int Fail(const char* message) {
+    std::fprintf(stderr, "host performance process: %s\n", message);
+    return 1;
+}
+
+}
+
+int main(int argc, char** argv) {
+    if (argc != 2) return Fail("usage: host_performance_process_tests <case>");
+    const std::string name = argv[1];
+    if (name == "exit" || name == "exit-without-handlers") {
+        if (StartProcessSession(Mode::On, std::make_unique<PrintingBackend>(Outcome::Started)) == nullptr) return Fail("an on session must exist");
+        std::fflush(stdout);
+        if (name == "exit") LibcExit_nid_no_patch(0);
+        LibcExitWithoutHandlers_nid_no_patch(0);
+    }
+    if (name == "refused") {
+        if (StartProcessSession(Mode::Auto, std::make_unique<PrintingBackend>(Outcome::Refused)) == nullptr) return Fail("an auto session must exist");
+        std::fflush(stdout);
+        LibcExit_nid_no_patch(0);
+    }
+    if (name == "off") {
+        if (StartProcessSession(Mode::Off, std::make_unique<PrintingBackend>(Outcome::Started)) != nullptr) return Fail("an off session must not exist");
+        std::puts("off left the backend alone");
+        std::fflush(stdout);
+        LibcExit_nid_no_patch(0);
+    }
+    if (name == "twice") {
+        StartProcessSession(Mode::On, std::make_unique<PrintingBackend>(Outcome::Started));
+        try {
+            StartProcessSession(Mode::On, std::make_unique<PrintingBackend>(Outcome::Started));
+        } catch (const std::logic_error&) {
+            std::puts("second session refused");
+            std::fflush(stdout);
+            LibcExit_nid_no_patch(0);
+        }
+        return Fail("a second session must be refused");
+    }
+    if (name == "environment") {
+        const char* value = std::getenv("APS5_GAME_MODE");
+        try {
+            StartFromEnvironment();
+        } catch (const std::invalid_argument& error) {
+            if (value != nullptr && std::strcmp(value, "bogus") == 0 && std::string(error.what()).find("APS5_GAME_MODE=bogus") != std::string::npos) {
+                std::puts("invalid value rejected by name");
+                return 0;
+            }
+            return Fail(error.what());
+        }
+        if (value != nullptr && std::strcmp(value, "bogus") == 0) return Fail("an invalid value must be rejected");
+        std::puts("environment accepted");
+        return 0;
+    }
+    return Fail("unknown case");
+}