improve clang support (33)

[Bruno Haible]

This set of patches fixes a number of warnings that I'm seeing when building
a POSIX testdir on MSVC/clang.


2020-08-16  Bruno Haible  <bruno@clisp.org>

        Fix "warning: 'WSASocketA' is deprecated: Use WSASocketW() instead".
        * lib/socket.c: Use WSASocketW, not WSASocketA.

        Fix "warning: format specifies type 'unsigned long'".
        * tests/test-nonblocking-writer.h (main_writer_loop): Cast dbgfprintf
        argument to match the format directive.

        Fix "warning: no case matching constant switch condition '0'".
        * tests/test-fcntl.c (check_flags): Add a 'default' case.

        Fix "warning: integer overflow in expression".
        * tests/test-strtol.c (main): Use an 'unsigned long' expression to
        remove a 'long' overflow.

        Fix "warning: "getpagesize" redefined".
        * tests/test-getcwd.c (getpagesize): Don't redefine if defined as a
        macro.

        Fix "warning: implicitly declaring library function 'strncasecmp'".
        * lib/strptime.c: Include <strings.h>.

        Fix "warning: 'snprintf' macro redefined".
        * lib/strerror_r.c (snprintf): Undefine before redefining.

        Fix "warning: address of array 'locale' will always evaluate to 'true'".
        * lib/nl_langinfo.c (ctype_codeset): Remove redundant NULL test.

        Fix "warning: '__stat64' macro redefined".
        * lib/glob.c (__stat64): Undefine also on MSVC/clang.

        Fix "warning: 'format' attribute argument not supported: rpl_printf".
        * lib/stdio.in.h (printf): Treat clang like GCC.

        Fix "warning: attribute declaration must precede definition" with clang.
        * lib/math.in.h (acosl, asinl, atanl, ceill, cosl, expl, fabsf, fabsl,
        floorl, fmodl, frexpf, frexpl, hypotf, hypotl, ldexpf, ldexpl, logl,
        log10l, modfl, sinl, sqrtl, tanl): Disable _GL_CXXALIASWARN invocation
        on non-glibc systems.
        * lib/netdb.in.h (gai_strerror): Likewise.
        * lib/stdio.in.h (snprintf, vfscanf, vscanf, vsnprintf): Likewise.
        * lib/sys_stat.in.h (fstat): Likewise.
        * lib/utime.in.h (utime): Likewise.

        Fix undesired warnings.
        * lib/sys_select.in.h: Disable all _GL_WARN_ON_USE invocations with
        clang.

0001-Fix-undesired-warnings.patch
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0002-Fix-warning-attribute-declaration-must-precede-defin.patch
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0003-Fix-warning-format-attribute-argument-not-supported-.patch
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0004-Fix-warning-__stat64-macro-redefined.patch
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0005-Fix-warning-address-of-array-locale-will-always-eval.patch
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0006-Fix-warning-snprintf-macro-redefined.patch
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0007-Fix-warning-implicitly-declaring-library-function-st.patch
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0008-Fix-warning-getpagesize-redefined.patch
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0009-Fix-warning-integer-overflow-in-expression.patch
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0010-Fix-warning-no-case-matching-constant-switch-conditi.patch
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0011-Fix-warning-format-specifies-type-unsigned-long.patch
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0012-Fix-warning-WSASocketA-is-deprecated-Use-WSASocketW-.patch
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