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4049. C <foo.h> headers not in freestanding

Section: 16.4.2 [organization] Status: New Submitter: Ben Craig Opened: 2024-01-26 Last modified: 2024-08-21

Priority: 3

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Discussion:

There are many C-ish <cfoo> headers in freestanding. There isn't anything that requires the matching C <foo.h> headers to be in freestanding.

[2024-08-21; Reflector poll]

Set priority to 3 after reflector poll. Some discomfort requiring errno.h and wchar.h to be freestanding in C++ when they are not in C23. string.h is not freestanding in C17, but is in C23 (but C++ is still based on C17). stdlib.h is "conditionally partially freestanding" in C23, but not in C17. Suggestion to incorporate this into P3348.

Proposed resolution:

This wording is relative to N4971.

  1. Modify 16.4.2.3 [headers] as indicated:

    -9- 17.14 [support.c.headers], C standard library headers, describes the effects of using the name.h (C header) form in a C++ program. The name.h form is the corresponding C header form.

  2. Modify 16.4.2.5 [compliance] as indicated:

    -2- A freestanding implementation has an implementation-defined set of headers. This set shall include at least the headers shown in Table 27 and the corresponding C header form (16.4.2.3 [headers]) of each of the C++ headers for C library facilities (Table 25) included in Table 27.