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      <base href="https://bugs.llvm.org/">
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - llvm-cov: macro constant in if expression lead to incorrect coverage"
   href="https://bugs.llvm.org/show_bug.cgi?id=45849">45849</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>llvm-cov: macro constant in if expression lead to incorrect coverage
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>Runtime Libraries
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>libprofile library
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>yangyibiao@hust.edu.cn
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>$ clang --version
clang version 11.0.0 (/home/yibiao/.cache/yay/llvm-git/llvm-project
871beba234a83a2a02da9dedbd59b91a1bfbd7af)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

$ clang -O0 -w -fcoverage-mapping -fprofile-instr-generate=small.profraw
small.c; ./a.out; llvm-profdata merge small.profraw -o small.profdata; llvm-cov
show a.out -instr-profile=small.profdata small.c > small.c.lcov; cat
small.c.lcov
    1|      1|#define N 6
    2|       |
    3|      1|int main() {
    4|      1|  if (10 < 6)
    5|      0|    return 1;
    6|      1|  if (10 < N)
    7|      1|    return 2;
    8|      1|}


N is a constant 6 which defined as macro in Line 1.
Line 7 is wrongly marked as executed. The execution count of Line 5 is correct. 

$ cat small.c
#define N 6

int main() {
  if (10 < 6)
    return 1;
  if (10 < N)
    return 2;
}</pre>
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