c++ - vector 下标超出范围？

Question

我正在编写自己的编程语言(用于学习)，但出现错误。

Debug Assertion Failed!
Program: C:/Path/MSVCP140D.dll
Line: 1232

Expression vector subscript out of range

For information how your progr... (Not important)

出错的函数:

Parser::Parser(std::vector<std::string> toks) {
    for (unsigned i = 0; i < toks.size(); i++) {
        if (toks[i++] + " " + toks[i] == "PRINT STRING:") { 
            std::cout << toks[i += 1] << std::endl;
        }

        if (toks[i++] + " " + toks[i] == "ASM STRING:") {
            std::cout << "FOUND ASM" << std::endl;
        }
    }
}

生成toks的函数:

Lexer::Lexer(std::string source){
    std::string tok = "";
    std::string string = "";
    int state = 0;

    for (int i = 0; i <= source.length(); i++) {
        tok += source[i];

        if (tok == " ") {
            if (state == 1) {
                string += tok;
            } else tok = "";
        } else if (tok == "\n") {
            tok = "";
        } else if (tok == "print") {
            tokens.push_back("PRINT");
            tok = "";
        } else if (tok == "asm") {
            tokens.push_back("ASM");
            tok = "";
        } else if (tok == "\"") {
            if (state == 0) {
                state = 1;
            } else if (state == 1) {
                tokens.push_back("STRING:");
                tokens.push_back(string);
                string = "";
                state = 0;
                tok = "";
            }
        } else if (state == 1) {
            string += source[i];
            tok = "";
        }
    }
}

输出:

toks that are generated: PRINTSTRING:print  expASMSTRING:ams  exp
toks one by one:
PRINT
STRING:
print exp
ASM
STRING:
ams exp

Answer 1

我相信你唯一想增加 i 的时间是在这里:

for (unsigned i = 0; i < toks.size(); i++)
//                                    ^^^

toks[i++] 然后 toks[i] 在没有检查的循环中会变得非常糟糕。应该是 toks[i + 1]，记住 i + 1 不能达到 toks.size()？同样的:toks[i += 1]。

也许你应该在循环体和这个:

for (unsigned i = 0; i + 2 < toks.size(); i += 3)

还有一个问题是:

for (int i = 0; i <= source.length(); i++)
//                ^^
//           should be <

不知道是不是这样