config: rename the OS define to CURL_OS to reduce collision risk

Reported-by: Jon Rumsey
Fixes #15455
Closes #15457

select: use poll() if existing, avoid poll() with no sockets

poll() on macOS 10.12 was deemed broken in 2016 when we discovered that
it misbehaves when provided with no sockets to wait f

select: use poll() if existing, avoid poll() with no sockets

poll() on macOS 10.12 was deemed broken in 2016 when we discovered that
it misbehaves when provided with no sockets to wait for. The
HAVE_POLL_FINE is used to mark a poll() implementation that behaves
correctly: it *should* still wait the timeout time.

curl has therefore opted to use select() on Apple operating systems ever
since. To avoid the risk that this or other breakage cause problems.

However, using select() internally is also bad because it suffers from
problems when using file descriptors beyond 1024.

This change makes poll() used if it is present, but if there is no
sockets to wait for it avoids using poll() and instead falls back to
select() - but without any sockets to wait for there is no 1024 problem.

This removes all previous special-handling involving HAVE_POLL_FINE.

ref: https://daniel.haxx.se/blog/2016/10/11/poll-on-mac-10-12-is-broken/

Closes #15096

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lib: remove use of RANDOM_FILE

It could previously be set with configure/cmake and used in rare cases
for reading randomness: with ancient mbedTLS or rustls without
arc4random.

lib: remove use of RANDOM_FILE

It could previously be set with configure/cmake and used in rare cases
for reading randomness: with ancient mbedTLS or rustls without
arc4random.

We now get randomness in this order:

1. The TLS library's way to provide random
2. On Windows: Curl_win32_random
3. if arc4random exists, use that
4. weak non-crytographically strong pseudo-random

Closes #14749

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build: prefer `USE_IPV6` macro internally (was: `ENABLE_IPV6`)

Before this patch, two macros were used to guard IPv6 features in curl
sources: `ENABLE_IPV6` and `USE_IPV6`. This patch ma

build: prefer `USE_IPV6` macro internally (was: `ENABLE_IPV6`)

Before this patch, two macros were used to guard IPv6 features in curl
sources: `ENABLE_IPV6` and `USE_IPV6`. This patch makes the source use
the latter for consistency with other similar switches.

`-DENABLE_IPV6` remains accepted for compatibility as a synonym for
`-DUSE_IPV6`, when passed to the compiler.

`ENABLE_IPV6` also remains the name of the CMake and `Makefile.vc`
options to control this feature.

Closes #13349

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build: delete `HAVE_STDINT_H` and `HAVE_INTTYPES_H`

We use `stdint.h` unconditionally in all places except one. These uses
are imposed by external dependencies / features. nghttp2, quic,

build: delete `HAVE_STDINT_H` and `HAVE_INTTYPES_H`

We use `stdint.h` unconditionally in all places except one. These uses
are imposed by external dependencies / features. nghttp2, quic, wolfSSL
and `HAVE_MACH_ABSOLUTE_TIME` do require this C99 header. It means that
any of these features make curl require a C99 compiler. (In case of
MSVC, this means Visual Studio 2010 or newer.)

This patch changes the single use of `stdint.h` guarded by
`HAVE_STDINT_H` to use `stdint.h` unconditionally. Also stop using
`inttypes.h` as an alternative there. `HAVE_INTTYPES_H` wasn't used
anywhere else, allowing to delete this feature check as well.

Closes #12275

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lib: remove TIME_WITH_SYS_TIME

It is not used in any code anywhere.

Ref: #11964
Closes #11975

build: delete checks for C89 standard headers

Delete checks and guards for standard C89 headers and assume these are
available: `stdio.h`, `string.h`, `time.h`, `setjmp.h`, `stdlib.h`,

build: delete checks for C89 standard headers

Delete checks and guards for standard C89 headers and assume these are
available: `stdio.h`, `string.h`, `time.h`, `setjmp.h`, `stdlib.h`,
`stddef.h`, `signal.h`.

Some of these we already used unconditionally, some others we only used
for feature checks.

Follow-up to 9c7165e96a3a9a2d0b7059c87c699b5ca8cdae93 #11918 (for `stdio.h` in CMake)

Closes #11940

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copyright: update all copyright lines and remove year ranges

- they are mostly pointless in all major jurisdictions
- many big corporations and projects already don't use them
- save

copyright: update all copyright lines and remove year ranges

- they are mostly pointless in all major jurisdictions
- many big corporations and projects already don't use them
- saves us from pointless churn
- git keeps history for us
- the year range is kept in COPYING

checksrc is updated to allow non-year using copyright statements

Closes #10205

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build: assume errno.h is always available

- Remove errno.h detection from all build configurations.

errno.h is a standard header according to C89.

Closes https://github.com

build: assume errno.h is always available

- Remove errno.h detection from all build configurations.

errno.h is a standard header according to C89.

Closes https://github.com/curl/curl/pull/9986

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build: assume assert.h is always available

- Remove assert.h detection from all build configurations.

assert.h is a standard header according to C89.

I had proposed this se

build: assume assert.h is always available

- Remove assert.h detection from all build configurations.

assert.h is a standard header according to C89.

I had proposed this several years ago as part of a larger change that
was abandoned.

Ref: https://github.com/curl/curl/issues/1237#issuecomment-277500720

Closes https://github.com/curl/curl/pull/9985

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Makefile.mk: portable Makefile.m32

Update bare GNU Make `Makefile.m32` to:

- Move objects into a subdirectory.
- Add support for MS-DOS. Tested with DJGPP.
- Add support for

Makefile.mk: portable Makefile.m32

Update bare GNU Make `Makefile.m32` to:

- Move objects into a subdirectory.
- Add support for MS-DOS. Tested with DJGPP.
- Add support for Watt-32 (on MS-DOS).
- Add support for AmigaOS.
- Rename `Makefile.m32` to `Makefile.mk`
- Replace `ARCH` with `TRIPLET`.
- Build `tool_hugehelp.c` proper (when tools are available).
- Drop MS-DOS compatibility macro `USE_ZLIB` (replaced by `HAVE_LIBZ`)
- Add support for `ZLIB_LIBS` to override `-lz`.
- Omit object files when building examples.
- Default `CC` to `gcc` once again, for convenience. (Caveat: compiler
name `cc` cannot be set now.)
- Set `-DCURL_NO_OLDIES` for examples, like autotools does.
- Delete `makefile.dj` files. Notice the configuration details and
defaults are not retained with the new method.
- Delete `makefile.amiga` files. A successful build needs a few custom
options. We're also not retaining all build details from the existing
Amiga make files.
- Rename `Makefile.m32` to `Makefile.mk` to reflect that they are not
Windows/MinGW32-specific anymore.
- Add support for new `CFG` options: `-map`, `-debug`, `-trackmem`
- Set `-DNDEBUG` by default.
- Allow using `-DOS=...` in all `lib/config-*.h` headers, syncing this
with `config-win32.h`.
- Look for zlib parts in `ZLIB_PATH/include` and `ZLIB_PATH/lib`
instead of bare `ZLIB_PATH`.

Note that existing build configurations for MS-DOS and AmigaOS likely
become incompatible with this change.

Example AmigaOS configuration:
```
export CROSSPREFIX=/opt/amiga/bin/m68k-amigaos-
export CC=gcc
export CPPFLAGS='-DHAVE_PROTO_BSDSOCKET_H'
export CFLAGS='-mcrt=clib2'
export LDFLAGS="${CFLAGS}"
export LIBS='-lnet -lm'
make -C lib -f Makefile.mk
make -C src -f Makefile.mk
```

Example MS-DOS configuration:
```
export CROSSPREFIX=/opt/djgpp/bin/i586-pc-msdosdjgpp-
export WATT_PATH=/opt/djgpp/net/watt
export ZLIB_PATH=/opt/djgpp
export OPENSSL_PATH=/opt/djgpp
export OPENSSL_LIBS='-lssl -lcrypt'
export CFG=-zlib-ssl
make -C lib -f Makefile.mk
make -C src -f Makefile.mk
```

Closes #9764

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tidy-up: delete parallel/unused feature flags

Detecting headers and lib separately makes sense when headers come in
variations or with extra ones, but this wasn't the case here. These we

tidy-up: delete parallel/unused feature flags

Detecting headers and lib separately makes sense when headers come in
variations or with extra ones, but this wasn't the case here. These were
duplicate/parallel macros that we had to keep in sync with each other
for a working build. This patch leaves a single macro for each of these
dependencies:

- Rely on `HAVE_LIBZ`, delete parallel `HAVE_ZLIB_H`.

Also delete CMake logic making sure these two were in sync, along with
a toggle to turn off that logic, called `CURL_SPECIAL_LIBZ`.

Also delete stray `HAVE_ZLIB` defines.

There is also a `USE_ZLIB` variant in `lib/config-dos.h`. This patch
retains it for compatibility and deprecates it.

- Rely on `USE_LIBSSH2`, delete parallel `HAVE_LIBSSH2_H`.

Also delete `LIBSSH2_WIN32`, `LIBSSH2_LIBRARY` from
`winbuild/MakefileBuild.vc`, these have a role when building libssh2
itself. And `CURL_USE_LIBSSH`, which had no use at all.

Also delete stray `HAVE_LIBSSH2` defines.

- Rely on `USE_LIBSSH`, delete parallel `HAVE_LIBSSH_LIBSSH_H`.

Also delete `LIBSSH_WIN32`, `LIBSSH_LIBRARY` and `HAVE_LIBSSH` from
`winbuild/MakefileBuild.vc`, these were the result of copy-pasting the
libssh2 line, and were not having any use.

- Delete unused `HAVE_LIBPSL_H` and `HAVE_LIBPSL`.

Reviewed-by: Daniel Stenberg

Closes #9652

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functypes: provide the recv and send arg and return types

This header is for providing the argument types for recv() and send()
when built to not use a dedicated config-[platfor].h file.

functypes: provide the recv and send arg and return types

This header is for providing the argument types for recv() and send()
when built to not use a dedicated config-[platfor].h file.

Remove the slow brute-force checks from configure and cmake.

This change also removes the use of the types for select, as they were
not used in code.

Closes #9592

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config: remove the check for and use of SIZEOF_SHORT

shorts are 2 bytes on all platforms curl runs and have ever run on.

Closes #9291

tidy-up: delete unused build configuration macros

Most of them feature guards:

- `CURL_INCLUDES_SYS_UIO` [1]
- `HAVE_ALLOCA_H` [2]
- `HAVE_CRYPTO_CLEANUP_ALL_EX_DATA` (unuse

tidy-up: delete unused build configuration macros

Most of them feature guards:

- `CURL_INCLUDES_SYS_UIO` [1]
- `HAVE_ALLOCA_H` [2]
- `HAVE_CRYPTO_CLEANUP_ALL_EX_DATA` (unused since de71e68000c8624ea13f90b136f8734dd0fb1bdc)
- `HAVE_DLFCN_H`
- `HAVE_DLOPEN`
- `HAVE_DOPRNT`
- `HAVE_FCNTL`
- `HAVE_GETHOSTBYNAME` [3]
- `HAVE_GETOPT_H`
- `HAVE_GETPASS`
- `HAVE_GETPROTOBYNAME`
- `HAVE_GETSERVBYNAME`
- `HAVE_IDN_FREE*`
- `HAVE_INET_ADDR`
- `HAVE_IOCTL`
- `HAVE_KRB4`
- `HAVE_KRB_GET_OUR_IP_FOR_REALM`
- `HAVE_KRB_H`
- `HAVE_LDAPSSL_H`
- `HAVE_LDAP_INIT_FD`
- `HAVE_LIBDL`
- `HAVE_LIBNSL`
- `HAVE_LIBRESOLV*`
- `HAVE_LIBUCB`
- `HAVE_LL`
- `HAVE_LOCALTIME_R`
- `HAVE_MALLOC_H`
- `HAVE_MEMCPY`
- `HAVE_MEMORY_H`
- `HAVE_NETINET_IF_ETHER_H`
- `HAVE_NI_WITHSCOPEID`
- `HAVE_OPENSSL_CRYPTO_H`
- `HAVE_OPENSSL_ERR_H`
- `HAVE_OPENSSL_PEM_H`
- `HAVE_OPENSSL_PKCS12_H`
- `HAVE_OPENSSL_RAND_H`
- `HAVE_OPENSSL_RSA_H`
- `HAVE_OPENSSL_SSL_H`
- `HAVE_OPENSSL_X509_H`
- `HAVE_PEM_H`
- `HAVE_POLL`
- `HAVE_RAND_SCREEN`
- `HAVE_RAND_STATUS`
- `HAVE_RECVFROM`
- `HAVE_SETSOCKOPT`
- `HAVE_SETVBUF`
- `HAVE_SIZEOF_LONG_DOUBLE`
- `HAVE_SOCKIO_H`
- `HAVE_SOCK_OPTS`
- `HAVE_STDIO_H`
- `HAVE_STRCASESTR`
- `HAVE_STRFTIME`
- `HAVE_STRLCAT`
- `HAVE_STRNCMPI`
- `HAVE_STRNICMP`
- `HAVE_STRSTR`
- `HAVE_STRUCT_IN6_ADDR`
- `HAVE_TLD_H`
- `HAVE_TLD_STRERROR`
- `HAVE_UNAME`
- `HAVE_USLEEP`
- `HAVE_WINBER_H`
- `HAVE_WRITEV`
- `HAVE_X509_H`
- `LT_OBJDIR`
- `NEED_BASENAME_PROTO`
- `NOT_NEED_LIBNSL`
- `OPENSSL_NO_KRB5`
- `RECVFROM_TYPE*`
- `SIZEOF_LONG_DOUBLE`
- `STRERROR_R_TYPE_ARG3`
- `USE_YASSLEMUL`
- `_USRDLL` (from CMake) [4]

[1] Related parts in `m4/curl-functions.m4` and `configure.ac` might
also be deleted.

[2] Related comment can possibly be deleted in
`packages/vms/generate_config_vms_h_curl.com`.

[3] There are more instances of this in autotools, but I did not dare to
touch those. Looked like it's used to detect socket support.

[4] This is necessary for MFC (Microsoft Foundation Class) DLLs to
force linking MFC components statically to the DLL. `libcurl.dll`
does not use MFC, so we can delete this define.
Ref: https://docs.microsoft.com/cpp/build/regular-dlls-statically-linked-to-mfc

Script that can help finding unused settings like above:
```shell

autoheader configure.ac # generate lib/curl_config.h.in

{
grep -o -E 'set\([A-Z][A-Z0-9_]{3,}' CMake/Platforms/WindowsCache.cmake | sed -E 's|set\(||g'
grep -o -E -h '#define +[A-Z][A-Z0-9_]{3,}' lib/config-*.h | sed -E 's|#define +||g'
grep -o -E '#cmakedefine +[A-Z][A-Z0-9_]{3,}' lib/curl_config.h.cmake | sed -E 's|#cmakedefine +||g'
grep -o -E '#undef +[A-Z][A-Z0-9_]{3,}' lib/curl_config.h.in | sed -E 's|#undef +||g'
} | sort -u | grep -v -F 'HEADER_CURL_' | while read -r def; do
c="$(git grep -w -F "${def}" | grep -v -E -c '(/libcurl\.tmpl|^lib/config-|^lib/curl_config\.h\.cmake|^CMakeLists\.txt|^CMake/Platforms/WindowsCache\.cmake|^packages/vms/config_h\.com|^m4/curl-functions\.m4|^acinclude\.m4|^configure\.ac)')"
if [ "${c}" = '0' ]; then
echo "${def}"
fi
done
```

Reviewed-by: Daniel Stenberg
Closes #9044

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copyright: make repository REUSE compliant

Add licensing and copyright information for all files in this repository. This
either happens in the file itself as a comment header or in the

copyright: make repository REUSE compliant

Add licensing and copyright information for all files in this repository. This
either happens in the file itself as a comment header or in the file
`.reuse/dep5`.

This commit also adds a Github workflow to check pull requests and adapts
copyright.pl to the changes.

Closes #8869

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Get rid of the unused HAVE_SIG_ATOMIC_T et. al.

It was added in 2006 but I see no evidence it was ever used.

configure/cmake: remove checks for unused gethostbyaddr and gethostbyaddr_r

Closes #7276

configure/cmake: remove unused define HAVE_PERROR

Closes #7276

configure/cmake: remove unused define HAVE_FORK

Closes #7276

configure/cmake: remove unused define HAVE_FDOPEN

Closes #7276

config: remove now-unused macros

Closes #7094

configure: remove use of RETSIGTYPE

This was previously defined by the obsolete AC_TYPE_SIGNAL macro,
which was removed in 2682e5f5. The deprecation text says

> Your code may sa

configure: remove use of RETSIGTYPE

This was previously defined by the obsolete AC_TYPE_SIGNAL macro,
which was removed in 2682e5f5. The deprecation text says

> Your code may safely assume C89 semantics that RETSIGTYPE is void.

So, remove it and just use void instead.

Closes #6861

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build: remove all traces of USE_BLOCKING_SOCKETS

libcurl doesn't behave properly with the define set

Closes #6655

build: delete unused feature guards

- `HAVE_STRNCASECMP`
- `HAVE_TCGETATTR`
- `HAVE_TCSETATTR`

Reviewed-by: Jay Satiro
Reviewed-by: Daniel Stenberg
Closes #6645