libunwind/test/libunwind_02.pass.cpp

   1 // -*- C++ -*-
   2 //===----------------------------------------------------------------------===//
   3 //
   4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   5 // See https://llvm.org/LICENSE.txt for license information.
   6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   7 //
   8 //===----------------------------------------------------------------------===//
   9
  10 // TODO: Figure out why this fails with Memory Sanitizer.
  11 // XFAIL: msan
  12
  13 // This test fails on older llvm, when built with picolibc.
  14 // XFAIL: clang-16 && LIBCXX-PICOLIBC-FIXME
  15
  16 #undef NDEBUG
  17 #include <assert.h>
  18 #include <stdlib.h>
  19 #include <unwind.h>
  20
  21 #define EXPECTED_NUM_FRAMES 50
  22 #define NUM_FRAMES_UPPER_BOUND 100
  23
  24 __attribute__((noinline)) _Unwind_Reason_Code callback(_Unwind_Context *context,
  25                                                        void *cnt) {
  26   (void)context;
  27   int *i = (int *)cnt;
  28   ++*i;
  29   if (*i > NUM_FRAMES_UPPER_BOUND) {
  30     abort();
  31   }
  32   return _URC_NO_REASON;
  33 }
  34
  35 __attribute__((noinline)) void test_backtrace() {
  36   int n = 0;
  37   _Unwind_Backtrace(&callback, &n);
  38   if (n < EXPECTED_NUM_FRAMES) {
  39     abort();
  40   }
  41 }
  42
  43 // These functions are effectively the same, but we have to be careful to avoid
  44 // unwanted optimizations that would mess with the number of frames we expect.
  45 // Surprisingly, slapping `noinline` is not sufficient -- we also have to avoid
  46 // writing the function in a way that the compiler can easily spot tail
  47 // recursion.
  48 __attribute__((noinline)) int test1(int i);
  49 __attribute__((noinline)) int test2(int i);
  50
  51 __attribute__((noinline)) int test1(int i) {
  52   if (i == 0) {
  53     test_backtrace();
  54     return 0;
  55   } else {
  56     return i + test2(i - 1);
  57   }
  58 }
  59
  60 __attribute__((noinline)) int test2(int i) {
  61   if (i == 0) {
  62     test_backtrace();
  63     return 0;
  64   } else {
  65     return i + test1(i - 1);
  66   }
  67 }
  68
  69 int main(int, char**) {
  70   int total = test1(50);
  71   assert(total == 1275);
  72   return 0;
  73 }