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PONeed to replace use of strcpy_s in C code used in iPhone project
 

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  1. PONeed to replace use of strcpy_s in C code used in iPhone project
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    <p>I have a C SDK I need to use in an iPhone project, and the example code was written for use with Visual Studio. It includes use of strcpy_s, which is a Microsoft-only string function.</p> <pre><code>file_header.header_size = FIT_FILE_HDR_SIZE; strcpy_s((FIT_UINT8 *)&amp;file_header.data_type, sizeof(".FIT"), ".FIT"); &lt;&lt; problem! </code></pre> <p>I've tried changing to strcpy and strncpy like so</p> <pre><code>strncpy((FIT_UINT8 *)&amp;file_header.data_type, ".FIT", sizeof(".FIT")); </code></pre> <p>But I get this warning: </p> <p>warning: pointer targets in passing argument 1 of '<strong>builtin</strong>_strncpy_chk' differ in signedness</p> <p>warning: pointer targets in passing argument 1 of '__inline_strncpy_chk' differ in signedness</p> <p>warning: call to <strong>builtin</strong>_strncpy_chk will always overflow destination buffer</p> <p>The struct file_header is this:</p> <pre><code>typedef struct { FIT_UINT8 header_size; // FIT_FILE_HDR_SIZE (size of this structure) FIT_UINT8 protocol_version; // FIT_PROTOCOL_VERSION FIT_UINT16 profile_version; // FIT_PROFILE_VERSION FIT_UINT32 data_size; // Does not include file header or crc. Little endian format. FIT_UINT8 data_type[4]; // ".FIT" } FIT_FILE_HDR; </code></pre> <p>FIT_UINT8 is typedef Unsigned char.</p> <p>So we can see that it is given an length of 4 in the typedef, and the strcpy_s takes the data_type by reference and copys ".FIT" to it. Where am I going wrong with strncpy? If you haven't guessed by now I'm not much of a C programmer :)</p> <p>Edit: this does not give me an error, but it is correct?</p> <pre><code>strncpy((void *)&amp;file_header.data_type, ".FIT", sizeof(file_header.data_type)); </code></pre>
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