⚠️ 原样重抛，类型一点没变

（本条路线统一用 g++ -std=c++17 -O0 -Wall 编译）中间那层接住之后又原样扔了出去：

#include <iostream>
#include <stdexcept>
#include <string>

static std::string path;
static void mark(const char *n) { if (!path.empty()) path += ">"; path += n; }

/* 中间这层管不了，就原样往上抛 —— 但顺手留个记号 */
static int middle(int v) {
    mark("middle");
    try {
        if (v < 0) throw std::invalid_argument("neg");
        return v;
    } catch (const std::exception &) {
        mark("caught");
        throw;                 /* 原样重抛，类型和内容都不变 */
    }
}

int main() {
    int ok = middle(5);
    int top_caught = 0;
    std::string msg;
    try {
        middle(-1);
    } catch (const std::invalid_argument &e) {
        top_caught = 1;
        msg = e.what();
    }
    std::cout << ok << "/" << top_caught << "/" << msg << "/" << path << "\n";
    return 0;
}