Besides global memory, threads also share a number of other attributes (i.e., these attributes are global to a process, rather than specific to a thread). These attributes include the following: process ID and parent process ID; process group ID and session ID; controlling terminal; process credentials (user and group IDs); open file descriptors; record locks created using fcntl(); signal dispositions; file system–related information: umask, current working directory, and root directory; interval timers (setitimer()) and POSIX timers (timer_create()); System V semaphore undo (semadj) values (Section 47.8); resource limits; CPU time consumed (as returned by times()); resources consumed (as returned by getrusage()); and nice value (set by setpriority() and nice()). Among the attributes that are distinct for each thread are the following: thread ID (Section 29.5); signal mask; thread-specific data (Section 31.3); alternate signal stack (sigaltstack()); the errno variable; floating-point environment (see fenv(3)); realtime scheduling policy and priority (Sections 35.2 and 35.3); CPU affinity (Linux-specific, described in Section 35.4); capabilities (Linux-specific, described in Chapter 39); and stack (local variables and function call linkage information).

摘自:《Linux编程接口:Linux和UNIX系统编程手册》，Michael Kerrisk，第619页

Besides global memory, threads also share a number of other attributes (i.e., these attributes are global to a process, rather than specific to a thread). These attributes include the following: process ID and parent process ID; process group ID and session ID; controlling terminal; process credentials (user and group IDs); open file descriptors; record locks created using fcntl(); signal dispositions; file system–related information: umask, current working directory, and root directory; interval timers (setitimer()) and POSIX timers (timer_create()); System V semaphore undo (semadj) values (Section 47.8); resource limits; CPU time consumed (as returned by times()); resources consumed (as returned by getrusage()); and nice value (set by setpriority() and nice()). Among the attributes that are distinct for each thread are the following: thread ID (Section 29.5); signal mask; thread-specific data (Section 31.3); alternate signal stack (sigaltstack()); the errno variable; floating-point environment (see fenv(3)); realtime scheduling policy and priority (Sections 35.2 and 35.3); CPU affinity (Linux-specific, described in Section 35.4); capabilities (Linux-specific, described in Chapter 39); and stack (local variables and function call linkage information).

摘自:《Linux编程接口:Linux和UNIX系统编程手册》，Michael Kerrisk，第619页

线程共享代码、数据段和堆，但不共享堆栈。

您说得很对，但是线程共享除堆栈之外的所有段。线程有独立的调用堆栈，但是其他线程堆栈中的内存仍然是可访问的，理论上你可以在其他线程的本地堆栈框架中保存内存指针(尽管你可能应该找到一个更好的地方来放置内存!)。

在进程中，所有线程共享系统资源，如堆内存等，而线程有自己的堆栈

所以你的ans应该是一个进程中所有线程共享的堆内存。

A process has code, data, heap and stack segments. Now, the Instruction Pointer (IP) of a thread OR threads points to the code segment of the process. The data and heap segments are shared by all the threads. Now what about the stack area? What is actually the stack area? Its an area created by the process just for its thread to use... because stacks can be used in a much faster way than heaps etc. The stack area of the process is divided among threads, i.e. if there are 3 threads, then the stack area of the process is divided into 3 parts and each is given to the 3 threads. In other words, when we say that each thread has its own stack, that stack is actually a part of the process stack area allocated to each thread. When a thread finishes its execution, the stack of the thread is reclaimed by the process. In fact, not only the stack of a process is divided among threads, but all the set of registers that a thread uses like SP, PC and state registers are the registers of the process. So when it comes to sharing, the code, data and heap areas are shared, while the stack area is just divided among threads.