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Asked: 2026-06-02T23:37:47+00:00

While porting a C++ Program from 32 to 64 bit under windows I realized

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While porting a C++ Program from 32 to 64 bit under windows I realized _tcslen is not supported and instead strlen/wcslen (for non-unicode/unicode) should be used. I started to wonder

  1. If wcslen is part of the ISO/IEC 14882:2003 C++ standard library. I see this function is supported both by g++ as well as VC++. Also in open group I found a reference stating The functionality described on this reference page is aligned with the ISO C standard but didn’t mention if its C89 or c99.
  2. Is it documented somewhere that _tcslen is not compatible with Win64? Even the MSDN Link doesn’t hint a thing.
  3. For Unicode can wcslen be used inadvertently instead of _tcslen?
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1 Answer

  1. Editorial Team
    1. Yes it is. Table 48 in section 21.4 gives wcslen as one of the functions declared in <cwchar>.
    2. _tcslen is also available when doing x64 builds.
    3. As long as _UNICODE is defined then _tcslen expands to wcslen. The only thing you gain by using _tcslen is that theoretically you can make an ANSI build of your application by flipping a switch; practically there is nothing you stand to gain from this (ANSI builds in 2012 are simply atrocious IMHO) and it takes actual work to make your build work both ways. I would not recommend it.
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