284. unportable example in 20.3.7, p6

Section: 23.14.7 [comparisons] Status: CD1 Submitter: Martin Sebor Opened: 2000-12-26 Last modified: 2016-02-10

Priority: Not Prioritized

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Discussion:

The example in 23.14.7 [comparisons], p6 shows how to use the C library function strcmp() with the function pointer adapter ptr_fun(). But since it's unspecified whether the C library functions have extern "C" or extern "C++" linkage [20.5.2.3 [using.linkage]], and since function pointers with different the language linkage specifications (10.5 [dcl.link]) are incompatible, whether this example is well-formed is unspecified.

Proposed resolution:

Change 23.14.7 [comparisons] paragraph 6 from:

[Example:

    replace_if(v.begin(), v.end(), not1(bind2nd(ptr_fun(strcmp), "C")), "C++");
  

replaces each C with C++ in sequence v.

to:

[Example:

    int compare(const char*, const char*);
    replace_if(v.begin(), v.end(),
               not1(bind2nd(ptr_fun(compare), "abc")), "def");
  

replaces each abc with def in sequence v.

Also, remove footnote 215 in that same paragraph.

[Copenhagen: Minor change in the proposed resolution. Since this issue deals in part with C and C++ linkage, it was believed to be too confusing for the strings in the example to be "C" and "C++". ]

[Redmond: More minor changes. Got rid of the footnote (which seems to make a sweeping normative requirement, even though footnotes aren't normative), and changed the sentence after the footnote so that it corresponds to the new code fragment.]