foo.cc: In function 'void Concat(char*, char*, char*)':
foo.cc:8:9: warning: unused variable 'len2' [-Wunused-variable]
    8 |     int len2 = strlen(s2);
      |         ^~~~
foo.cc:9:12: warning: 'char* strncpy(char*, const char*, size_t)' specified bound depends on the length of the source argument [-Wstringop-truncation]
    9 |     strncpy(result, s1, len1 - 1);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:7:22: note: length computed here
    7 |     int len1 = strlen(s1);
      |                ~~~~~~^~~~

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