PVS-Studio warning V814 for Putty

static void tell_str(FILE * stream, char *str)
{
    unsigned int i;
    for (i = 0; i < strlen(str); ++i)
      tell_char(stream, str[i]);
}

This suspicious code was found in Putty project by PVS-Studio static code analyzer.
Warning message is:
V814 Decreased performance. Calls to the 'strlen' function have being made multiple times when a condition for the loop's continuation was calculated. pscp.c 82

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