使用getcontext / setcontext切换堆栈

我试图了解getcontext / setcontext是否可以在特定方案中正常工作。

我可以看到如何使用setcontext（）将堆栈展开回历史记录中的某个位置。

#include  #include  int rollback = 0; ucontext_t context; void func(void) { setcontext(cp); } int main(void) { getcontext(&context); if (rollback == 0) { printf("getcontext has been called\n"); rollback++; func(); } else { printf("setcontext has been called\n"); } } 

但是我想知道在放松之后你是否可以重新回到未来的某个地方？ 我想这取决于getcontext()调用捕获堆栈的副本，​​我无法在文档中找到确切的详细信息。

 #include  #include  int rollback = 0; int backToFuture = 0; ucontext_t context; ucontext_t futureContext; void func(void) { // Some complex calc if (some-condition) { getcontext(&futureContext); // After returning I want to come back // here to carry on with my work. if (backToFuture == 0) { setcontext(&context); // rewind to get stuff-done } } // Finishe work } int main(void) { getcontext(&context); if (rollback == 0) { printf("getcontext has been called\n"); rollback++; func(); // eventually always return here. } else { printf("setcontext has been called\n"); // Do specialized work that needed to be done // May involve function calls. // // I worry that anything the adds new stack frames // will disrupt the saved state of futureContext // // But without detailed information I can not be sure // if this is an allowed senario. backToFuture = 1; setcontext(&futureContext); } } 

Answer 1

getcontext不复制堆栈，它只转储寄存器（包括堆栈指针）和一些像信号掩码等的上下文数据。

当你跳下堆栈时，它会使顶层上下文无效。 即使你不做任何函数调用，也要考虑可以在那里执行的信号处理程序。 如果要在两个堆栈之间跳转，则需要makecontext 。

我添加了变量，certificate您的代码无效：

 void func(void) { // Some complex calc if (1) { volatile int neverChange = 1; getcontext(&futureContext); // After returning I want to come back // here to carry on with my work. printf("neverchange = %d\n", neverChange); if (backToFuture == 0) { setcontext(&context); // rewind to get stuff-done } } // Finishe work } 

在我的机器上，它导致：

 getcontext has been called neverchange = 1 setcontext has been called neverchange = 32767