编译简单C++程序时来自llvm的无法解释的剖面数据

Question

当分析下面的main.cpp文件时，我得到"test1完成“行的"0”，指示当我期望得到"1“时该行没有被执行

main.cpp

#include <cassert>
#include <iostream>

using namespace std;

void test1() {
  cout << "test1 start" << endl;
  string pdx;
  assert(pdx == "");
  cout << "test1 complete" << endl;
}

int main() {
  test1();
  cout << "Done." << endl;
}

要分析代码，我使用的脚本是：

#!/bin/bash

clang++ -g -std=c++11 -fprofile-instr-generate -fcoverage-mapping main.cpp

# Execute the program
./a.out

llvm-profdata merge default.profraw -output=merged.profraw

llvm-cov report -show-functions=1  ./a.out -instr-profile=merged.profraw main.cpp

llvm-cov show ./a.out -instr-profile=merged.profraw 

rm a.out *.profraw

# $ clang++ --version
# clang version 13.0.1 (Red Hat 13.0.1-2.module+el8.6.0+987+d36ea6a1)
# Target: x86_64-unknown-linux-gnu
# Thread model: posix
# InstalledDir: /usr/bin

如果去掉下面的行，就会得到预期的结果

  string pdx;
  assert(pdx == "");

分析main.cpp的输出

$ ./check-code-coverage.sh 
test1 start
test1 complete
Done.
File '/home/cssuwbstudent/pisan/bitbucket/pisan342/check-overage/main.cpp':
Name                        Regions    Miss   Cover     Lines    Miss   Cover  Branches    Miss   Cover
-------------------------------------------------------------------------------------------------------
_Z5test1v                         1       0 100.00%         6       1  83.33%         0       0   0.00%
main                              1       0 100.00%         4       0 100.00%         0       0   0.00%
-------------------------------------------------------------------------------------------------------
TOTAL                             2       0 100.00%        10       1  90.00%         0       0   0.00%
    1|       |#include <cassert>
    2|       |#include <iostream>
    3|       |
    4|       |using namespace std;
    5|       |
    6|      1|void test1() {
    7|      1|  cout << "test1 start" << endl;
    8|      1|  string pdx;
    9|      1|  assert(pdx == "");
   10|      0|  cout << "test1 complete" << endl;
   11|      1|}
   12|       |
   13|      1|int main() {
   14|      1|  test1();
   15|      1|  cout << "Done." << endl;
   16|      1|}

$

任何洞察力都将不胜感激。

Answer 1

这是一个错误，应该报告给发出叮当声的人。