<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/60958>60958</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Clang -E incorrect -Wunicode diagnostic
        </td>
    </tr>

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

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

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

<pre>
    Discovered entirely accidentally while trying to work around #60792

Given
```
$ cat hdr.h 
.macro test uniq
    mov $\uniq, %eax
.endm

$ cat src.c
#include "hdr.h"

$ clang-15 -E src.c -o out.i
In file included from src.c:1:
./hdr.h:2:11: warning: \u used with no following hex digits; treating as '\' followed by identifier [-Wunicode]
    mov $\uniq, %eax
          ^
```

But there's are no strings here, and no context AFAICT where it would be legitimate to interpret `\u` as a unicode escape in the first place.

But if I rename src.c to src.S, it behaves differently
```
$ cp src.c src.S
$ clang-15 -E src.S -o out.i
$
```
and completes with no complaints.

Clearly this diagnostic is conditional on the file extension (which isn't great behaviour to start with), but I don't think it's a legitimate diagnostic for `*.c` files in the first place either.

It's worth saying for completeness that macros written entirely at the C level work fine, because they have to be written as 
```
asm (".macro test uniq; mov $\\uniq, %eax; .endm");
```
with the backslash needing to be escaped, rather than the u.
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJyMVcGO4jgQ_RpzKREFhwQ4cAB6WPV5VtqzY1eS2nFs1q6Q5u9XTtK9zHSPtK1WCGX7-dV7VYWKkVqHeBTlWZQvKzVw58NROfPoutuq9uZxfKGo_R0DGkDHFNA-QGlNBh0rax8wdmQRODzItcAeRh9-gAp-cAaELKp8d5AifxH5aX7-QXd0S6DKl__5q9yCVgydCVkHcyzrlQ4eGCPD4OifOQoA0Ps7CLkV5WWKywsIWaJ6W86hM_3zte_gMehMv4cKctoOBkFIOd0qpPx0yCrXrjclrL_Nh2HtwQ-c0bzn1UGTFFigDDTB98s1xWkjigUrE_I631GcZFpJSzCq4Mi16TVlAkNEAyNxB85D4631Y9K1wzcw1BJHUZyBAypOYRVByJ0oL0Lult1ooH7AZA81hAFEeV7_NTjS3qAoX_6vgPDxJ8pvX9s1Pc8DA3cYUMhdBBUwEY8cyLUR5vgFlDMprL1jfGM4XU-vlz9hTMtADKMfrIEawWJLTL1iTJVEjjHcAjKkO8vLIKo8paxgSQcwanVL0icK0FCIDDerNGa_UqQGXiGgUz0uLrKfXr4nfsRQY6fuGMFQ02BAx_bx-yK9LRgzwG9L5fsvpZLU_gozyaN9f7PIGD_cnyKKHMefsrlYVME-gDtKbFXrfGTSQDHpa4jJO2XBv2tiEfCN0UXyDoTcjx3pDig6IXcMbSqlOXnyQ5hUYRV4YiHkIalTDwyvYPx8gjtyP4B49vvZsicyjQ-TafKU6eRaohG_8AmQUvH8lODrDD36wB1ENc2VhPeukMMYgTvFMM2GCGMgZnRP82kqSbiAxTvaeSI15KZSrFGrIWLa8IBkeUq5xg-Q1FJfehT7pJ6Q8tNIKs5PvfS5nYozzNNIyiRocf4Sf3I9sa6V_hGtih04RLMM1fq91k0CDiqJljSYBR2ylTkW5lAc1AqPm2q32-yrw75Ydced3uS7WtWbpt5U20LVldnti7zZ75t9UVRqRUeZyyKXspCbTSWLTO4PuN1sZVUZVRdqJ7Y59opsZu29z3xoVxTjgMcqP5T7lVU12jj9gEjpcIRpMaVavqzCMZ1Z10MbxTa3FDn-h8LEFo-X1DKpX8hpHwJqho9p9VRQqyHYY8d8i2meyquQ15a4G-pM-17Ia0JdPta34P9GzUJeJy5RyOvE9d8AAAD__wQmJuU">