fuzz: Link all targets once

src/test/fuzz/fuzz.cpp

@@ -5,6 +5,7 @@
 #include <test/fuzz/fuzz.h>
 
 #include <test/util/setup_common.h>
+#include <util/check.h>
 
 #include <cstdint>
 #include <unistd.h>
@@ -12,6 +13,36 @@
 
 const std::function<void(const std::string&)> G_TEST_LOG_FUN{};
 
+std::map<std::string_view, std::tuple<TypeTestOneInput, TypeInitialize>>& FuzzTargets()
+{
+    static std::map<std::string_view, std::tuple<TypeTestOneInput, TypeInitialize>> g_fuzz_targets;
+    return g_fuzz_targets;
+}
+
+void FuzzFrameworkRegisterTarget(std::string_view name, TypeTestOneInput target, TypeInitialize init)
+{
+    const auto it_ins = FuzzTargets().try_emplace(name, std::move(target), std::move(init));
+    Assert(it_ins.second);
+}
+
+static TypeTestOneInput* g_test_one_input{nullptr};
+
+void initialize()
+{
+    if (std::getenv("PRINT_ALL_FUZZ_TARGETS_AND_ABORT")) {
+        for (const auto& t : FuzzTargets()) {
+            std::cout << t.first << std::endl;
+        }
+        Assert(false);
+    }
+    std::string_view fuzz_target{Assert(std::getenv("FUZZ"))};
+    const auto it = FuzzTargets().find(fuzz_target);
+    Assert(it != FuzzTargets().end());
+    Assert(!g_test_one_input);
+    g_test_one_input = &std::get<0>(it->second);
+    std::get<1>(it->second)();
+}
+
 #if defined(PROVIDE_MAIN_FUNCTION)
 static bool read_stdin(std::vector<uint8_t>& data)
 {
@@ -24,14 +55,10 @@ static bool read_stdin(std::vector<uint8_t>& data)
 }
 #endif
 
-// Default initialization: Override using a non-weak initialize().
-__attribute__((weak)) void initialize()
-{
-}
-
 // This function is used by libFuzzer
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size)
 {
+    static const auto& test_one_input = *Assert(g_test_one_input);
     const std::vector<uint8_t> input(data, data + size);
     test_one_input(input);
     return 0;
@@ -48,6 +75,7 @@ extern "C" int LLVMFuzzerInitialize(int* argc, char*** argv)
 __attribute__((weak)) int main(int argc, char** argv)
 {
     initialize();
+    static const auto& test_one_input = *Assert(g_test_one_input);
 #ifdef __AFL_INIT
     // Enable AFL deferred forkserver mode. Requires compilation using
     // afl-clang-fast++. See fuzzing.md for details.