[compiler-rt] [sanitizer] Pre-commit disabled test for fork (PR #75257)

[Florian Mayer via llvm-commits]

================
@@ -0,0 +1,86 @@
+// RUN: %clangxx -O0 %s -o %t && %env_tool_opts=die_after_fork=0 %run %t
+
+// UNSUPPORTED: *
+
+// Forking in multithread environment is unsupported. However we already have
+// some workarounds, and will add more, so this is the test.
+
+#include <assert.h>
+#include <pthread.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include "sanitizer_common/sanitizer_specific.h"
+
+static const size_t kBufferSize = 1 << 20;
+
+static void *background(void *arg) { return nullptr; }
+
+pthread_barrier_t bar;
+
+void CanDeadLock() {
+  // Don't bother with leaks, we try to trigger allocator or lsan deadlock.
+  __lsan::ScopedDisabler disable;
+  char *volatile p = new char[10];
+  __lsan_do_recoverable_leak_check();
+  delete[] p;
+}
+
+// Prevent stack buffer cleanup by instrumentation.
+#define NOSAN __attribute__((no_sanitize("address", "hwaddress", "memory")))
+
+NOSAN static void *inparent(void *arg) {
+  fprintf(stderr, "inparent %d\n", gettid());
+
+  char t[kBufferSize];
+  make_mem_bad(t, sizeof(t));
+
+  pthread_barrier_wait(&bar);
+
+  for (;;)
+    CanDeadLock();
+
+  return 0;
+}
+
+NOSAN static void *inchild(void *arg) {
+  char t[kBufferSize];
+  check_mem_is_good(t, sizeof(t));
+  CanDeadLock();
+  return 0;
+}
+
+int main(void) {
+  pid_t pid;
+
+  pthread_barrier_init(&bar, nullptr, 2);
+  pthread_t thread_id;
+  while (pthread_create(&thread_id, 0, &inparent, 0) != 0) {
+  }
+  pthread_barrier_wait(&bar);
+
+  pid = fork();
+  switch (pid) {
+  case -1:
+    perror("fork");
+    return -1;
+  case 0:
+    while (pthread_create(&thread_id, 0, &inchild, 0) != 0) {
+    }
+    break;
+  default: {
+    fprintf(stderr, "fork %d\n", pid);
+    int status;
+    while (waitpid(-1, &status, __WALL) != pid) {
+    }
+    assert(WIFEXITED(status) && WEXITSTATUS(status) == 0);
+    break;
+  }
+  }
+
+  return 0;
+}
----------------
fmayer wrote:

nit: newline at EOL

https://github.com/llvm/llvm-project/pull/75257