diff --git a/src/libmain/shared.hh b/src/libmain/shared.hh index 0cc56d47d..3c37fd627 100644 --- a/src/libmain/shared.hh +++ b/src/libmain/shared.hh @@ -113,5 +113,25 @@ struct PrintFreed /* Install a SIGSEGV handler to detect stack overflows. */ void detectStackOverflow(); +/* Pluggable behavior to run in case of a stack overflow. + + Default value: defaultStackOverflowHandler. + + This is called by the handler installed by detectStackOverflow(). + + This gives Nix library consumers a limit opportunity to report the error + condition. The handler should exit the process. + See defaultStackOverflowHandler() for a reference implementation. + + NOTE: Use with diligence, because this runs in the signal handler, with very + limited stack space and a potentially a corrupted heap, all while the failed + thread is blocked indefinitely. All functions called must be reentrant. */ +extern std::function stackOverflowHandler; + +/* The default, robust implementation of stackOverflowHandler. + + Prints an error message directly to stderr using a syscall instead of the + logger. Exits the process immediately after. */ +void defaultStackOverflowHandler(siginfo_t * info, void * ctx); } diff --git a/src/libmain/stack.cc b/src/libmain/stack.cc index b0a4a4c5d..10f71c1dc 100644 --- a/src/libmain/stack.cc +++ b/src/libmain/stack.cc @@ -1,4 +1,5 @@ #include "error.hh" +#include "shared.hh" #include #include @@ -29,9 +30,7 @@ static void sigsegvHandler(int signo, siginfo_t * info, void * ctx) ptrdiff_t diff = (char *) info->si_addr - sp; if (diff < 0) diff = -diff; if (diff < 4096) { - char msg[] = "error: stack overflow (possible infinite recursion)\n"; - [[gnu::unused]] auto res = write(2, msg, strlen(msg)); - _exit(1); // maybe abort instead? + nix::stackOverflowHandler(info, ctx); } } @@ -67,5 +66,12 @@ void detectStackOverflow() #endif } +std::function stackOverflowHandler(defaultStackOverflowHandler); + +void defaultStackOverflowHandler(siginfo_t * info, void * ctx) { + char msg[] = "error: stack overflow (possible infinite recursion)\n"; + [[gnu::unused]] auto res = write(2, msg, strlen(msg)); + _exit(1); // maybe abort instead? +} }