<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/69939>69939</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Constructor size is twice as large on Clang17.0.2 with MTE enabled
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          P1119r1m
      </td>
    </tr>
</table>

<pre>
    To reproduce the problem 2 files should be created:
- main.c
```
typedef int (*ctor_t)(void);

#define __constructor__    \
    __attribute__((__used__)) __attribute__((__section__(".ctors")))

#define DECLARE_CONSTRUCTOR(fn)    \
    static ctor_t ctor_##fn __constructor__ = fn

static int init_FIRST_func(void) { return 0; }
static int init_SECOND_func(void) { return 0; }

DECLARE_CONSTRUCTOR(init_FIRST_func);
DECLARE_CONSTRUCTOR(init_SECOND_func);

int main(int argc, char *argv[]) {
    (void)argc;
    (void)argv;
 return 0;
}
```

- build.sh
```
#!/bin/bash

## CONFIG

# 16.0.6 (llvmorg-v16.0.6 tag) - THE PROBLEM COULD NOT BE REPRODUCED
CLANG_DIR=... !!! USE YOUR PATH !!! ...
# 17.0.0 (llvmorg-v17-init tag) - THE PROBLEM COULD NOT BE REPRODUCED
CLANG_DIR=... !!! USE YOUR PATH !!! ...
# 17.0.2 (llvmorg-17.0.2 tag) - THE PROBLEM COULD BE REPRODUCED
CLANG_DIR=... !!! USE YOUR PATH !!! ...
# 17.0.3 (llvmorg-17.0.3 tag) - THE PROBLEM COULD BE REPRODUCED
CLANG_DIR=... !!! USE YOUR PATH !!! ...

CC="${CLANG_DIR}/bin/clang"
LLD="${CLANG_DIR}/bin/ld.lld"
OBJDUMP="${CLANG_DIR}/bin/llvm-objdump"

CC_FLAGS="-march=armv8.3-a+memtag -fsanitize=memtag"  # COMMENT THIS CODE TO "FIX" THE ISSUE!

## COMPILE
${CC} ${CC_FLAGS} -c main.c -o main.o

## LINK
${LLD} main.o -o ./main.syms

## ANALYZE <BEGIN>

echo -e "\n\n>>>>>>>> Show functions' addresses in compiled *.o file <<<<<<<<"
${OBJDUMP} -dS main.o | grep '<init_'

echo -e "\n\n>>>>>>>> Show Clang version <<<<<<<<"
${CC} --version

echo -e "\n\n>>>>>>>> Show contstructors' code in final binary <<<<<<<<"
${OBJDUMP} -dS -j ".ctors" main.syms

## ANALYZE <END>
```

The output for the "source build.sh" run command is following:
```
$ source build.sh
...
0000000000220230 <ctor_init_SECOND_func>:
  220230: f4 01 21 00   .word   0x002101f4 <---- NOTE: 16 bytes (and this is a problem, IMHO)
  220234: 00 00 00 00 .word   0x00000000
  220238: 00 00 00 00   .word   0x00000000
  22023c: 00 00 00 00   .word   0x00000000
```

In case of using "Clang17.0.0" from the "llvmorg-v17-init" tag:
```
0000000000220228 <ctor_init_SECOND_func>:
  220228: f4 01 21 00   .word   0x002101f4 <---- NOTE: 8 bytes
  22022c: 00 00 00 00   .word 0x00000000
```

</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzEV99v4jgQ_mvMyyhRsCmBBx4gCS13FCp-SLf3EjmOA14lMbIdet2__uQk_GjLbnu7ujtkaGLPN_lmvonHpVqLXcn5CN1N0F3YoZXZSzV66na7Q9UtOolMX0YbCYoflEwrxsHsORyUTHJeAIZM5FyD3ssqTyHhwBSnhqeIjJEXIm_sQEFF6bLmDvW9dtS35uXAU56BKA0gPEB4zIxUsUF4iPDgKEVqr8ikBTe_mKQ8EyWHOGay1EZVNSgGAEB3QWNlb-KYGqNEUhkex7X7QRxXmqf2bojw8LaF5swIWbYT2LXeNcK4wdhxk00YBfPxKoqD5WK9WW2DzXKF8CAr7XPeMtOGGsGgCbb5gzBBmGTlu6gQCSErr5_Zom3SRClMPJ2t1ps4q0p2SRogfwKKm0qV4CEyAeSHt9HrKFguwk_Dm9_bwb5jc9HuB4BXBN6qbWnaAqqNDVC1YwgHwPZUAcJjqnbHpnBb0pccX4KpQeR7S8fL0lXALYdz1K_r9lTaSSXy1NX720ZW0S7C08TSnyb0bHdZJhAsF9PZ_ZsF6PZdz-1bonl-LKTaOcd2ytCdDdWBzUMET6vlZB49QrDczkNYLDcwiWAVPa2W4TaIWu7BfLy4j8PZCpHQdV2oSdkB23UEX5bbFTyNNw9X867rXlHxXc_1XlPxHavc_8QFX3NpZ37A5F9iQd6xIP8hi8ZBgEhYb0w95E8u7vzwXHQsp-XOmtSA-Tz8EJGnbp6nZ8hy8lu4fXz6GJYfC0cmX9OqOJzBJ5rxdD6-Xzc-nIIqtkckpKo4DlziUIQnBS8M3YGTaVoKI75xRMJmDmFs31f7njw-RosNbB5mawiWYQSbJSCMp7M_rI3N-Gy93kY2Vbfessen2Tw6zdVhBMgP4XTdUvRDcFjbscCRzZW84XA-W_x-7c2m1g9be4t0EZ7Wd_ql0DccjBfj-Zc_I0AkmET3swUi0bUVZ3sJDrcRorugrL8kujlgvZfPYLdP27Y0wj7QNFVca65BlMBkcRA5T-1-6cq6Ydun3h5n6eqoTurbtKTrU3TID2Cn-AEQ9hEJ6k3cXv4K_cAWKhy50kKWn6XXSOg4LeyXCDBZmlPXrXPIZMpt-jJR0hwSUVL18pN5c77C9UECPlkX0SK8VMWtBrTZc5CVOVQGMqnqgxnCWMtKMX7pTRiDquoyKGiZgtCQyTyXz6LcnU9p71pXD966qRfOO5B3_mDsYeJZvvWB5V1Ltzken3pvY4zIGLIeeF3AXfA8AHCfpUoBwPvL83DX62Y969BxHMd2EusBun1IXgzXdt-1cZi90DYYejqM2nPB7PFheT6htY_rWbTnXcb1w5rPK_vBW3v4CME-j7ip46wERjUHmUGlRbmzKtYvRNN7rYKZksVJ4Ld92K7brfI7Yr6WCg_-gVR48FNSDRqlXnn6bo4-yFAnHZF0SIa0w0fd_nDg-QNM-p39qD_gGWEZ79E0S3op85KEde94xj0yuKNDvyNGVpuu_fYxueu7nkd5glnC-gM_9XmGeh4vqMhdm1BXql1HaF3xUX84JMNOThOe6_rfIoxL_gz1Yr2fhB01qhteUu006nm50EZfvBhhcj4KLqd40OIbt7VqngXjQDXkVO04yBIuMmN4FmYPj5sIeEmTnKedSuWjvTEHbWXBU4SnO2H2VeIyWbQ999R6D0p-5cwgPK1paoSndRh_BwAA__-wy7H6">