<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/109707>109707</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [LLD][COFF] `start-lib` / `end-lib` incorrectly discards symbols referenced in the same library
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            lld
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          yuzhy8701
      </td>
    </tr>
</table>

<pre>
    When linking in a library with `start-lib` and `end-lib`, `lld-link` would discard a symbol unless it is already seen in the prior objects. It discards the symbol even if the symbol is referenced in a latter object from the same library (latter as the command line order).

## A simple case to repro (Powershell on Windows):

1. Setup

    ```powershell
 Set-Content -Path .\hello-time.h -Value @"
    #ifndef LIB_HELLO_TIME_H_
    #define LIB_HELLO_TIME_H_
    
    #include <string>
    
    std::string get_localtime();
    
 #endif
    "@
    
    Set-Content -Path .\hello-time.cc -Value @"
    #include "hello-time.h"
    #include <ctime>
    #include <string>
    
    std::string get_localtime() {
      std::time_t result = std::time(nullptr);
      return std::asctime(std::localtime(&result));
    }
    "@
    
 Set-Content -Path .\hello-greet.h -Value @"
    #ifndef MAIN_HELLO_GREET_H_
    #define MAIN_HELLO_GREET_H_
    
 #include <string>
    
    std::string get_greet(const std::string &thing);
    
    #endif
    "@
    
    Set-Content -Path .\hello-greet.cc -Value @"
    #include "hello-time.h"
    #include "hello-greet.h"
    #include <string>
    
    std::string get_greet(const std::string& who) {
      return "Hello " + who + "; " + get_localtime();
    }
    "@
    
    Set-Content -Path .\hello-world.cc -Value @"
    #include "hello-greet.h"
 #include <iostream>
    #include <string>
    
    int main(int argc, char** argv) {
      std::cout << get_greet("world") << std::endl;
      return 0;
    }
    "@
    ```

2. The following succeeds:

    ```powershell
    If (Test-Path 'out') {
        Remove-Item -Path 'out' -Recurse -Force -Verbose
    }
 New-Item -Path 'out' -ItemType Directory
    
    clang-cl.exe /c 'hello-time.cc' /Fo'out/hello-time.obj'
    clang-cl.exe /c 'hello-greet.cc' /Fo'out/hello-greet.obj'
    clang-cl.exe /c 'hello-world.cc' /Fo'out/hello-world.obj'
    
    lld-link.exe /OUT:'out/hello-world.exe' `
        out/hello-world.obj `
 '/start-lib' `
        out/hello-greet.obj `
        out/hello-time.obj `
        '/end-lib'
    ```

3. The following fails with error: `lld-link: error: relocation against symbol in discarded section: ?get_localtime@@YA?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@XZ`

 ```powershell
    $ErrorActionPreference = "Stop"
    
    If (Test-Path 'out') {
        Remove-Item -Path 'out' -Recurse -Force -Verbose
    }
    New-Item -Path 'out' -ItemType Directory
    
 clang-cl.exe /c 'hello-time.cc' /Fo'out/hello-time.obj'
 clang-cl.exe /c 'hello-greet.cc' /Fo'out/hello-greet.obj'
    clang-cl.exe /c 'hello-world.cc' /Fo'out/hello-world.obj'
    
    lld-link.exe /OUT:'out/hello-world.exe' `
        out/hello-world.obj `
 '/start-lib' `
        out/hello-time.obj `
        out/hello-greet.obj `
        '/end-lib'
    ```

**Note that the only difference between success and fail cases is the object order between `start-lib` and `end-lib`.** I'm able to reproduce  with the latest llvm version (19.1.0).
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzsWEtv2zgX_TX05sKGRPmlhReOHX0NkD7Qpu03szEo6tpiS5EGScX1_PoB9XAsx3GSaYDZDBDEwuXhIe9Dh5di1oqNQpyR0RUZLXusdLk2s335V76fToKwl-psP_ueowIp1E-hNiAUMJAiNczsYSdcDmQcWMeM60uRknEATGXehiprLIQuvEFKb1A_PWanS5lBJixnJgMGdl-kWkKpJFoLwoGwwKRBlu3BIiq_rMsRtkZoAzr9gdzZAdy4lsNWww0N3vsZ62OTsGBwjQYVx6xxgjmHLRmsjS7qCazAg4OEThsYq1fguii8g1IoBG0yNITGAxIsSTBv_tOI0AjmYEWxlQicWQSnweDWaE_4Se_Q2BylBK3gu1CZ3llCYxLNj3nCAXxBV26PbQDgI1n_bQ88zeAXdP2FVg6Vg_4n5nIYkNHCA3TfiQIHOfS_MVkikGFAKD3ipJFYqwzXcHtztXp3fXv7cXV38_569W7VAWW49n5fAnU4FZdlhkCihXVGqA2Jrs9Brcu889G8RsEG3UpqzqTfNaHTKjhXj2YSGqHKxPp4TepdO7PEs7Hh_FJwWkcoPQ7nk7Bowautd9x903gAmRwF5GiKh6wcGLSldECiZXeI0Kkqpdw6cxpUAIOuNOoBzyxvphxM3V2M61U802mGJstns3IpJRuD6F5Sr-_nNx-aWvzf5-vruycq9jLsUE6_k6Bqy4ROuVbWPUIQOna5JzxfyvVm36Sa69C9aTm3sCYrF8r-baNG6Bh2uT5T7k2pEkrf-Z35ByD0yqOrX7_F6OpgflZQXlCuz4R9p43MXhn2R_HsBlNo6wyy4p_KiFAOCiYUoVP_yMyG-6OY58wQOid07k33l8SE69JryIJEi062CKWVv37nfnqNOExDlcnz2hK8IuztOXd8ANIB3OUIay2l3vkasiXniJk9OTwvH5QAcLP2R_EdWlcnktCJLh2hkzPhAPiMhb7H_o3DAk7w0P-MvDQWoZ9owxH639Ck2uI5Nz_g7gkSb73bbxGWwiB32uzPZZRLpjZ9Lgf4y5dRwj1F5xDzZIQmiW65k6Nhnf7wHr6ErlWRp_jq8VcQtu_HU4T1-Cnhw1PbPbbUH7_e-ZyfI8FfWK0yDrpZPLvcEazKfvLQyz7HcYjBZVgb-seoesG2Ue74fa74o9PiXzMhbd2EozHakGjeabSj-YPdoBdAJ7QCtmGiUtumNVZtE40ZWOQeUzFFSVc3hwEZBn_MSZTMv5EoIXSYMiv4qhGhYbD8Wpu9wqycYcJZbyXDwEtDNb2ZyGS1G22acVqPHmD___PE98tvM6HDa-_ovNr8p0OnX_U_hNIvTm-7avwvCwHA72nBWwrBfyrwWyrw9Ov9Qq14pQrUR_cH7RBczlx1K9VK7iET67bsU3Q7f2uuTkdrqyu5F4vqMmr9ZbiaVd98q1vsYcqzt_lB0zvcEDopgKXy4XablRyh1iPPL5lD60DK-wLu0VivPYROw3gQDgJ_be5lsyiLo5j1cBZO6CQMp_E47uWz4TjE0XQ9joZ8lAbriMXxOmNsGE3SkIZZ0BMzGtBhENMojMNxMBmEYRhhMBryeDjmMYvJMMCCCTnwqw-02fSEtSXOwiCeBJOeZClKW332oFTWjcxo2TMzD--n5cYLlxTW2QcCJ5ysvpTc3i7JaElGV4uPSUJGy0cxIzTpxgyE4tr4l7nKU_PFotbf0w8Tp98geqWRs9y5bdXj0ITQZCNcXqYDrgtCE7-_5qe_NdqnlNCk8tYSmjQO38_o3wEAAP__9RAouw">