<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/57708>57708</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            `CLANG_RESOURCE_DIR` doesn't change install destination of target `clang-resource-headers`
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

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

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

<pre>
    For example, building clang with cmake option `-D CLANG_RESOURCE_DIR=../lib/clang/current`
```
$ cat main.c
#include <stdarg.h>
int main(void) {return 0;}
$ clang -c main.c
main.c:1:10: fatal error: 'stdarg.h' file not found
#include <stdarg.h>
         ^~~~~~~~~~
1 error generated
```
Search paths from `clang -v -c main.c`:
```
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk/usr/local/include"
ignoring nonexistent directory "/usr/local/bin/../lib/clang/current/include"
ignoring nonexistent directory "/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/include
 /Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk/usr/include
 /Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk/System/Library/Frameworks (framework directory)
```
I noticed that
https://github.com/llvm/llvm-project/blob/7cddf9cad18a65217c8ba0661fefcf78d841a16b/clang/lib/Headers/CMakeLists.txt#L423
which is the default value of `CLANG_RESOURCE_DIR`.
If I understand the purpose of`CLANG_RESOURCE_DIR` correctly, these headers should be installed to `CLANG_RESOURCE_DIR/include`. 
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJytVdtu4zYQ_RrphbAgkbYkP-gh8aUN6u0CcQv0bUGRI4sNLQok5cR_36HkOAkQL7btGrJ4nZkzc2ZGtZHnamssgRd-7DVEdEXqQWmpugMRmuP7WfmWiCN_AmJ6r0xHojydrclqd_f7L98eN_uvfz6uNt_WD48RWydJRLda1fgepcM4WAudR6EoXUfpXZhMz7SkcyK4J0euukS87jHVCT1IIBFbOS-5PSRtxDbTseqm6xEtT0bJiC5JVNxb8IPtSBqx-6hYv1M-ejETHyxc5uwuC3-UuSMN91wTsNbYsIxocTVMC9IoDaQznjRm6OQPwSSvv2ixiYrbz3g5myyTA3RguQf5abD2wK1oSc9960hjzTFwcXHw9M7HPHj0qQZ16IwN5HamgxflPFJDpLIgvLFn9JoiZTtVW27POFvDCbTpweJ8ZY5H3smd6uAPY7TDrf36tzB84eLr_q-MJk4-4XJw4bo2gmscLyEKmn8cwUcVdeB6-53c-o9W_qefb-Jby4_wbOyTuwJ4nxyUJgE8JW7iz3luvSMtWHjj6UMyhfts87375Gagr8c_hcafrXV_Ri6ON6KH-svmdfVGF1b4p8n8ECpSCZDEt9xPe633vQtRolt8Dti8hjoRJljU-vQ6zHpr_kblIbm0CSlVCCmbpeAyK3m-oFkhypqneZ410IimKGU5z3iWv8--KRd_BS7BBk9XX7BJ7jDXXOJfUDXbzSmbUD23CnlUDoECkdDwQXty4nrAptqEIv6km-ZpcnGzIQ8Euw5a8RjjUUc_2N64IH1LmAhjQ_z0OTR1lMHb7YSVuNYMWpIaiOpQp9YhhOYGjrccQEQkhirLc5YuWJnnsayYXLIlj73yGqqbWKQBhzVceCJaDN7VLsbCedXx8buCkcBEP4C_drWZBWcGK2B2QY4H8WB19a9ZVs4NEEhaFEVaxm21bDhkvKHzvA5MN2zO6jyFJSuKol40aax5DdpV0eIeK7eDZzKqCPW9WMeqoiml6TJjaUHnNE-aMq0btgCWcbnMeR3NU8BmrJOAIzH2ENtqhFQPB4eHekyT6yF3DjsWwGgO9fPBt8ZWPcfqwohpTPJ4tF-N-P8BIQJpAA">