<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/143951>143951</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Incorrect warning message
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          Bill-Gray
      </td>
    </tr>
</table>

<pre>
    (Compiles correctly,  no security ramifications,  so prioritize accordingly.  May be an easy fix, though.)

In clang 18.1 and later (but not in 17.0.1 or earlier), compiling the following : 
```c
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>

int main( const int argc, const char **argv)
{
   char buff[9];

   assert( argc == 2);
   snprintf( buff, sizeof( buff), "%8.2f", atof( argv[1]));
   printf( "'%s'\n", buff);
 snprintf( buff, sizeof( buff), "%+8.2f", atof( argv[1]));
   printf( "'%s'\n", buff);
   return( 0);
}
```
gets me the following warning for the second `snprintf()`.  I think this is due to an assumption that the '+' will be added in,  resulting in a nine-byte (plus `\0` terminator) output.  Tested via the godbolt.org [Compiler Explorer](https://godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(filename:'1',fontScale:14,fontUsePx:'0',j:1,lang:c%2B%2B,selection:(endColumn:2,endLineNumber:15,positionColumn:1,positionLineNumber:1,selectionStartColumn:2,selectionStartLineNumber:15,startColumn:1,startLineNumber:1),source:'%23include+%3Cstdio.h%3E%0A%23include+%3Cstdlib.h%3E%0A%23include+%3Cassert.h%3E%0A%0Aint+main(+const+int+argc,+const+char+**argv)%0A%7B%0A+++char+buff%5B9%5D%3B%0A%0A+++assert(+argc+%3D%3D+2)%3B%0A+++snprintf(+buff,+sizeof(+buff),+%22%258.2f%22,+atof(+argv%5B1%5D))%3B%0A+++printf(+%22!'%25s!'%5Cn%22,+buff)%3B%0A+++snprintf(+buff,+sizeof(+buff),+%22%25%2B8.2f%22,+atof(+argv%5B1%5D))%3B%0A+++printf(+%22!'%25s!'%5Cn%22,+buff)%3B%0A+++return(+0)%3B%0A%7D%0A'),l:'5',n:'0',o:'C%2B%2B+source+%231',t:'0')),k:33.333333333333336,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:compiler,i:(compiler:clang1810,filters:(b:'0',binary:'1',binaryObject:'1',commentOnly:'0',debugCalls:'1',demangle:'0',directives:'0',execute:'1',intel:'0',libraryCode:'0',trim:'1',verboseDemangling:'0'),flagsViewOpen:'1',fontScale:14,fontUsePx:'0',j:1,lang:c%2B%2B,libs:!(),options:'',overrides:!(),selection:(endColumn:37,endLineNumber:6,positionColumn:37,positionLineNumber:6,selectionStartColumn:37,selectionStartLineNumber:6,startColumn:37,startLineNumber:6),source:1),l:'5',n:'0',o:'+x86-64+clang+18.1.0+(Editor+%231)',t:'0')),k:33.333333333333336,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:output,i:(compilerName:'x86-64+clang+17.0.1+(assertions)',editorid:1,fontScale:14,fontUsePx:'0',j:1,wrap:'1'),l:'5',n:'0',o:'Output+of+x86-64+clang+18.1.0+(Compiler+%231)',t:'0')),k:33.33333333333333,l:'4',n:'0',o:'',s:0,t:'0')),l:'2',n:'0',o:'',t:'0')),version:4).
```
<source>:12:4: warning: 'snprintf' will always be truncated; specified size is 9, but format string expands to at least 10 [-Wformat-truncation]
   12 |    snprintf( buff, sizeof( buff), "%+8.2f", atof( argv[1]));
      |    ^
```
Thank you.  I'm quite impressed with this compiler!
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzMWF-P4jgS_zTmpdQocQiBBx5I6D6NdLdz0u7dPTtJAd5xbM526GY__ansdCAM27d9mpO21YKkXH9t16-qEM7Jg0bcsLxk-W4men80dlNKpZ7-YsVlVpv2smF8VZnuJBU6aIy12Hh1YbwC0AYcNr2V_gJWdHIvG-Gl0S6sOgMnK42VXv6GIJrG2Fbqg7rMAf4mLlAjCA0o3AX28o1E_NH0h-Oc8TVLtizZftHQKKEPkK7mKQjdghIeLTC-qnsP2niQGtJinsxTMBZQWCXRkjyvoAlOS30Af0TYG6XMK72xbAukf5nE_4ZeeCZ1o_oWgWWV86008yPLnh8tKVk_XhPOofXjWrKV2kMnpGZ8BY3Rjtz1IOyhif4RpTkKCmjL-FbYw3mIvShZsgWIq3W_37O8XLN8x7IyqgaAaI50k0Zg2Y5lO-CkIRvEnT5Zqf2emIIWXoGTv6G5oYS9Ypwznq_mfB-eKhA-8gSf8jIl28R61X3VHEQKxnNHX3mlBx3v-qPEJ31hvPy_ugNg0fc2nE0yklmxu70aLNke0Dvo8O4OvQqr6XtvbFhx2BjdAlsmN2GS1mUyB_gC_ij1N_p0IB20PYI3dPuFc313opwBfxQ-6ArOl4wX8CqVCmnSttgC3aOK3Ha98mRcahCgpcan-uJJbnVSvSMnWF6R--DRdlILbygnwPT-1Ps5wC_oPLZwliIYPJi2NsrPjT0Ay8sh2S08v52UsWjDZq-O3p8cy7aMvzD-ciMTCNkhLKUh7NXvvxxZtm1Mi8-tDF5VMqyu9lKhFh2GtyINe1DtjfY_N0IRNV0MhH84_PtbZEsi26-0zHhFUEHqGc9p_8JH5VBhQxsc7aBuK6P6jl7pVqBu_yo1_tR3NVrSkzNenYyTJDJypjfEKfuthZ-9sH6ifbr0vSE3kUjfKfcmKC2c6W0zbA_F9g484arkV8ziefbMeE7Y9JApoteHXCOO3XIFNGO8HPCM8TLgF-NlpA-odkMn7Aoqb7Ft0FaUw1MZ_wfemKI5YR3P6dblWXl1YOQekW-0GxzfDR8lj5ayOyOT1BxskcMjCo3UdVygzSEsekfG8EYLAxxF8-fgcTp4vH5s-9byoCgdTpJwangOYDVaGX35kZGEvPiThTMiMeNlcseSF7vhqYjRqJgDecx9PUECE9-qWwQoh8yJhGyAFn8rF4OsvrFsm2XzbPK3vJpcfGAyvhA-Jg-0V49hMOLsFQRHSrYNfU-6SknbXiqPNmLvqp5Yr6UW9jIBzUj6Wv-KjZ8sNKbrUPuvWl0mOlqs-0MllHIT9hY7oQ8Kp7yS2j95Rjch4xs2vZ-Ct9Qe1YRLydoKe6lMO1Xqrewmome0tXG4ix5Ifbjfzr0SB_dPia9fT6h_eMlQsnY3h0UGzSn2tTdnbc5orWzxnvWDgpMVDyrO8lHBCZwPK87y9ytOEPqg5Cy_qzhR4hHjpOSkfzjzGC_fVsun5YIwPWwuL6l5nych_1bvZX_MxfWfJh1jd_R9Mv40diXfRxYmjxhZrElx-BmCwhCsbIe79smr-WrF6fZq_8ET-DqEURKkf3wY1QhA__Nx_IjTuAmM_1clj4TPaF3MtwXj6_ldA09D23CRn2lreeDLtu89fBgHeXEtqUPfLdSruDhqv73tdSM8tiwrwZ2wkXuJbRheqJtfx-HC0zDQCQ_OW-rO8e0kdOtCo-9BoXAe0oQa7Kd_Rc6nQTH5nu_iUJJyYEUFn5_dPjsvAbwbYvnz3Zb9chT6G1xMT7ML40UH_-6lR5DdyaJz2MKr9Mc4zlyrWDprN1m7ztZihpu0WKyLPOeLbHbcrBPM8iTJ9-uiWNfNsl4nTS6SfVIXok7zdCY3POF5skx5uk4Kns2zBDFdNe1y3Sb1ap-xRYKdkGqu1LmjoWMmnetxky6ydZ7OlKhRufAzBucaXyGs0l7ku5ndkNBT3R8cWyRKOu-uarz0Cjdf9PDDxjjYdeicOOCst2pzN_lIf-zreWM6xl9Iz_D1dLIm1Fz-Eqw7xl8G984b_p8AAAD__6ug2SU">