chore(3p/nix): unvendor tvix 0.1 r/4098

Nothing is using this now, and we'll likely never pick this up again,
but we learned a lot in the process.

Every now and then this breaks in some bizarre way on channel bumps
and it's just a waste of time to maintain that.

Change-Id: Idcf2f5acd4ca7070ce18d7149cbfc0d967dc0a44
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5632
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: lukegb <lukegb@tvl.fyi>
Autosubmit: tazjin <tazjin@tvl.su>

1 files changed, 0 insertions, 75 deletions

diff --git a/third_party/nix/src/libmain/stack.cc b/third_party/nix/src/libmain/stack.cc
deleted file mode 100644
index 628b6313a89c..000000000000
--- a/third_party/nix/src/libmain/stack.cc
+++ /dev/null
@@ -1,75 +0,0 @@
-#include <csignal>
-#include <cstddef>
-#include <cstdlib>
-#include <cstring>
-
-#include <unistd.h>
-
-#include "libutil/types.hh"
-
-namespace nix {
-
-static void sigsegvHandler(int signo, siginfo_t* info, void* ctx) {
-  /* Detect stack overflows by comparing the faulting address with
-     the stack pointer.  Unfortunately, getting the stack pointer is
-     not portable. */
-  bool haveSP = true;
-  char* sp = nullptr;
-#if defined(__x86_64__) && defined(REG_RSP)
-  sp = (char*)(static_cast<ucontext_t*>(ctx))->uc_mcontext.gregs[REG_RSP];
-#elif defined(REG_ESP)
-  sp = (char*)((ucontext_t*)ctx)->uc_mcontext.gregs[REG_ESP];
-#else
-  haveSP = false;
-#endif
-
-  if (haveSP) {
-    ptrdiff_t diff = static_cast<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?
-    }
-  }
-
-  /* Restore default behaviour (i.e. segfault and dump core). */
-  struct sigaction act;
-  sigfillset(&act.sa_mask);
-  act.sa_handler = SIG_DFL;
-  act.sa_flags = 0;
-  if (sigaction(SIGSEGV, &act, nullptr) != 0) {
-    abort();
-  }
-}
-
-void detectStackOverflow() {
-#if defined(SA_SIGINFO) && defined(SA_ONSTACK)
-  /* Install a SIGSEGV handler to detect stack overflows.  This
-     requires an alternative stack, otherwise the signal cannot be
-     delivered when we're out of stack space. */
-  stack_t stack;
-  stack.ss_size = 4096 * 4 + MINSIGSTKSZ;
-  static auto stackBuf = std::make_unique<std::vector<char>>(stack.ss_size);
-  stack.ss_sp = stackBuf->data();
-  if (stack.ss_sp == nullptr) {
-    throw Error("cannot allocate alternative stack");
-  }
-  stack.ss_flags = 0;
-  if (sigaltstack(&stack, nullptr) == -1) {
-    throw SysError("cannot set alternative stack");
-  }
-
-  struct sigaction act;
-  sigfillset(&act.sa_mask);
-  act.sa_sigaction = sigsegvHandler;
-  act.sa_flags = SA_SIGINFO | SA_ONSTACK;
-  if (sigaction(SIGSEGV, &act, nullptr) != 0) {
-    throw SysError("resetting SIGSEGV");
-  }
-#endif
-}
-
-}  // namespace nix