Pass build options directly via `COMPILE_DEFINTIONS` and
`LINK_LIBRARIES`, instead of "tunneling" them through `CMAKE_FLAGS`.
The latter method breaks when passing `Threads::Threads` as library via
`CMAKE_REQUIRED_LIBRARIES`, while also being complex and fragile.
Example:
```
-- Performing Test HAVE_FSETXATTR_5
CMake Error at bld/CMakeFiles/CMakeTmp/CMakeLists.txt:27 (target_link_libraries):
Target "cmTC_3386e" links to:
Threads::Threads
but the target was not found. Possible reasons include:
* There is a typo in the target name.
* A find_package call is missing for an IMPORTED target.
* An ALIAS target is missing.
CMake Error at CMake/Macros.cmake:51 (try_compile):
Failed to generate test project build system.
Call Stack (most recent call first):
CMakeLists.txt:1684 (curl_internal_test)
```
Ref: https://github.com/curl/curl/actions/runs/23792043930/job/69329796592?pr=21168#step:38:318
Note: a side-effect is no longer passing C compiler flags (e.g.
`CMAKE_REQUIRED_FLAGS`) to the _linker_. This should not be an issue,
though CMake is passing them during its built-in detections.
Ref: https://cmake.org/cmake/help/v3.18/command/try_compile.htmlCloses#21176
To allow simplifying the binutils ld hack, by chaining the original
imported target to curl's local duplicate target. Also to allow linking
to dependencies' native imported targets via their CMake Configs, which
will always be hooked up to a `CURL::` interface, and may also be
chained upstream.
Fixing (seen on Linux with simplified binutils hack via #20839):
```
Requires:
Requires.private: libzstd openssl zlib
Libs: -L${libdir} -lcurl
-Libs.private: -lcrypto -lssl -lz -lzstd
+Libs.private: -lOpenSSL::Crypto -lZLIB::ZLIB -lcrypto -lssl -lz -lzstd
Cflags: -I${includedir}
Cflags.private: -DCURL_STATICLIB
Error: Process completed with exit code
```
Ref: https://github.com/curl/curl/actions/runs/22768301699/job/66041980258?pr=20839
Note this makes it possible to run into an infinite loop because CMake
allows cyclic dependencies. It isn't added by curl's CMake script nor by
any dependencies as defined by default, but may happen in theory with
custom-created targets. In such case CMake automatically stops with
an error at 1000 iterations. I find it overkill to add custom protection
for it.
Cherry-picked from #20814
Cherry-picked from #20839Closes#20840
- also query `INTERFACE_COMPILE_DEFINITIONS` and
`INTERFACE_COMPILE_OPTIONS`.
To further sync clang-tidy manual command-lines with the C compiler
command-lines generated by CMake. In practice this adds `-I` options
(via `INTERFACE_COMPILE_OPTIONS`) to the end of the command-line for
dependency header directories. It does not change the outcome of
clang-tidy runs.
- limit querying `COMPILE_DEFINITIONS` and `COMPILE_OPTIONS` to the top
target, the test itself. To not include options such as
`-DCURL_HIDDEN_SYMBOLS` and `-fvisibility=hidden` (when set) via
the libcurl shared lib.
To sync with the actual C compiler command-line.
- drop redundant `unset()`.
- rename local function to be more specific.
Follow-up to d9386a2f8e#20759Closes#20829
This CMake global custom option tells it to find dependencies as cmake
Configs first, and only then look for `Find*` modules. This may result
in `find_package()` succeeding, but without actually creating `CURL::*`
imported targets the curl build scripts are expecting.
For dependencies with curl-specific, local, `Find*` modules, we always
want to use them, via the module detection method, and never a
Config-based detection. Ensure this by passing the `MODULE` option to
`find_package()` and `find_dependency()` to make them use `Find*`
modules unconditionally, making them work as expected with the
`CMAKE_FIND_PACKAGE_PREFER_CONFIG=ON` option set.
curl uses local Find modules for all dependencies except OpenSSL and
ZLIB. The latter two keep using either CMake's built-in Find modules or
Config method as before this patch.
Also:
- apply the same change to `curl-config.cmake`. To fix consuming curl
with this option set.
Authored-by: Valerie Snyder
Ref: #20764
Follow-up to 16f073ef49#16973
- GHA/distcheck: add a job testing both building and consuming curl with
this option set. (takes 15 seconds)
Use custom NGHTTP2 configuration for an extra twist (not required
to trigger this issue.)
Follow-up to fcde8d7e37#20773
Reported-by: Valerie Snyder
Fixes#20729Closes#20784
I thought a macro is necessary to have `get_directory_property()` and
`CMAKE_CURRENT_SOURCE_DIR` work on the correct directory, but it turns
out they do work the same when used in a function.
Closes#20760
To avoid a system include masking a custom directory, and e.g. picking
up system OpenSSL headers from `/usr/include` on Linux, instead of the
correct ones from a custom header directory, move system include
directories to the back of the header path list. Also to match what
CMake seems to be doing for the C compiler command-lines it generates.
CMake seems to use `-I`, while for these invocations we stick with
`-isystem` just in case.
This area remains fragile and likely not the final issue.
Fixing (seen in GHA/linux H3 c-ares):
```
Error while processing bld/tests/libtest/lib1521.c.
/usr/include/openssl/macros.h:147:4: error: "OPENSSL_API_COMPAT expresses an impossible API compatibility level" [clang-diagnostic-error]
Found compiler error(s).
147 | # error "OPENSSL_API_COMPAT expresses an impossible API compatibility level"
| ^
FAILED: [code=1] tests/libtest/CMakeFiles/libtests-clang-tidy
```
Ref: https://github.com/curl/curl/actions/runs/22468472670/job/65079885471?pr=20751
Bug: https://github.com/curl/curl/pull/20751#issuecomment-3970180687
Cherry-picked from #20751Closes#20759
Pass system directories with `-isystem` to avoid clang-tidy parsing
3rd-party and system headers with `HeaderFilterRegex: '.*' enabled.
Also:
- drop rule exception no longer necessary.
- sync normal vs. system header path order with compiler invocation.
- tidy up `set()` syntax.
- clear a temporary variable.
Bug: https://github.com/curl/curl/pull/20670#issuecomment-3940840176
Follow-up to e088e10454#17705
Cherry-picked from: #20720Closes#20724
By passing to clang-tidy the C compiler with `--target` and sysroot
options, if any.
Fixing (GHA/windows, linux-mingw, CM clang-tidy):
```
lib/curl_setup.h:841:10: error: 'io.h' file not found [clang-diagnostic-error]
841 | #include <io.h>
| ^~~~~~
Found compiler error(s).
FAILED: [code=1] tests/server/CMakeFiles/servers-clang-tidy bld/tests/server/CMakeFiles/servers-clang-tidy
cd tests/server && /usr/bin/clang-tidy --config-file=.clang-tidy.yml
--warnings-as-errors=* --checks=-clang-diagnostic-unused-function first.c getpart.c util.c dnsd.c [...]
-- <-D-options> <-I-options> <cflags>
```
For reference, this is CMake's built-in clang-tidy invocation:
```
/usr/local/bin/cmake -E __run_co_compile --tidy="/usr/bin/clang-tidy;--config-file=.clang-tidy.yml;
--warnings-as-errors=*;--extra-arg-before=--driver-mode=gcc" --source=lib/curl_fopen.c
-- /usr/bin/clang --target=x86_64-w64-mingw32 <-D-options> <-I-options> <cflags>
```
Also:
- bump cmakelint `--max-statements`. Needs 59 after this patch.
- use undocumented CMake variables:
- `CMAKE_C_COMPILE_OPTIONS_TARGET` for `--target=`
- `CMAKE_C_COMPILE_OPTIONS_SYSROOT` for `--sysroot=`
Cherry-picked from #20631Closes#20640
Fix bigger and smaller kinks in how clang-tidy is configured and used.
Sync behavior more between autotools and cmake, lib/src and tests. Bump
clang-tidy minimum version and prepare logic to allow using clang-tidy
to a fuller extent.
- move clang-tidy settings from builds to a new `.clang-tidy.yml`.
To make it easy to see and edit checks at one place. Also to allow
using the `--checks=` option internally to silence tests-specific
checks. (clang-tidy does not support multiple `--check=` options via
the command-line.)
Use explicit `--config-file=` option to point to the configuration.
- .clang-tidy.yml: link to documentation.
- suppress `clang-diagnostic-nullability-extension` due to a false
positive in libtests with `CURL_WERROR=ON` and `PICKY_COMPILER=OFF`.
- .clang-tidy.yml: enable `portability-*`, `misc-const-correctness`.
- drop `--quiet` clang-tidy option by default to make its working a bit
more transparent. The extra output is minimial.
- consistently use double-dashes in clang-tidy command-line options.
Supported by clang-tidy 9.0.0+ (2019-09-19). Before this patch single
and double were used arbitrarily.
- src/tool_parsecfg: silence false positive `clang-analyzer-unix.Stream`.
Seen with clang 18 + clang-tidy 19 and 20 (only with autotools.)
- INTERNALS: require clang-tidy 14.0.0+. For the `--config-file` option.
- INTERNALS: recommend clang-tidy 19.1.0+, to avoid bogus
`clang-analyzer-valist.Uninitialized` warnings. (bug details below)
autotools:
- allow configuring the clang-tidy tool via `CLANG_TIDY` env.
Also to use in GHA to point to a suffixed clang-tody tool.
- fix to pass CFLAGS to lib, src sources.
(keep omitting them when using a non-clang compiler.)
- fix to pass `--warnings-as-errors=*` in quotes to avoid globbing.
cmake:
- fix to not pass an empty `-I` to clang-tidy.
- fix to pass CFLAGS (picky warnings) to clang-tidy for test sources.
(keep omitting them when using a non-clang compiler.)
- fix to disable `clang-diagnostic-unused-function` for test sources.
(tests have static entry points, which trigger this check when
checking them as individidual sources.)
- fix forwarding `CURL_CLANG_TIDYFLAGS` to clang-tidy.
- force disable picky warnings when running clang-tidy with a non-clang
compiler. To not pass these flags when checking lib and src.
CI:
- GHA/linux: avoid clang-tidy bug by upgrading to v19, and drop the
workaround.
- GHA/linux: switch to clang from gcc in the clang-tidy job. Using gcc
doesn't allow passing CFLAGS to clang-tidy, making it less effective.
(My guess this was one factor contributing to this job often missing
to find certain issues compared to GHA/macos.)
I recomment using clang-tidy with a clang compiler, preferably the same
version or one that's compatible. Other cases are best effort, and may
fail if a C flag is passed to clang-tidy that it does not understand.
Picky warnings are mostly omitted when using a non-clang compiler,
reducing its usefulness.
Details and reproducer for the v18 (and earlier) clang-tidy bug,
previously affecting the GHA/linux job:
clang-tidy <=18 emits false warnings way when passing multiple C sources
at once (as done with autotools):
```sh
cat > src1.c <<EOF
#include <string.h>
static void dummy(void *p) { memcmp(p, p, 0); }
EOF
cat > src2.c <<EOF
#include <stdarg.h>
void vafunc(int option, ...)
{
va_list param;
va_start(param, option);
if(option)
(void)va_arg(param, int);
va_end(param);
}
EOF
/opt/homebrew/opt/llvm@18/bin/clang-tidy --checks=clang-analyzer-valist.Uninitialized src1.c src2.c
# src2.c:7:11: warning: va_arg() is called on an uninitialized va_list [clang-analyzer-valist.Uninitialized]
```
Follow-up to e86542038d#17047Closes#20605
This fixes curl using libraries if `CURL_{BROTLI|ZLIB|ZSTD}` is set to
`OFF` but the library was found in a parent project that includes curl.
Closes#20147
- simplify gathering header directories and compiler definitions
recursively.
- handle the case when the cmake directory object doesn't define header
directories or compiler definitions.
- honor more corners cases:
- `INTERFACE_INCLUDE_DIRECTORIES` of the initial target.
- handle no header directory for initial target.
- de-duplicate header directories and compiler redefinitions to mimic
CMake.
- drop unnecessary `unset()`s.
Note that the order of header directories remains different compared to
how CMake passes them to the compiler when building tests. The order is
already different in the test target `INCLUDE_DIRECTORIES` property,
preventing to reproduce the exact CMake order. The distinction between
`-I` and `-isystem` is also missing from target properties.
Cherry-picked from #17768Closes#17814
Fix `curl_add_clang_tidy_test_target` generating an invalid option for
`clang-tidy` if the tested target has no custom macro definition.
Current build doesn't hit this case, but a pending PR does.
Fixing:
```
[...] -Ilib -Itests/client -DCURL_HIDDEN_SYMBOLS -DHAVE_CONFIG_H -D_definitions_t-NOTFOUND
```
error: ISO C99 requires whitespace after the macro name [clang-diagnostic-c99-extensions,-warnings-as-errors]
Cherry-picked from #17768Closes#17813
To make `ninja units-clang-tidy` target work without manually building
core components first.
Also rename the clang-tidy test target generator macro to align its name
with the built-in `add_custom_target()` function.
Follow-up to c9bb9cd165#17750Closes#17810
Replace existing `mk-unity.pl` `--embed` workaround with running
`clang-tidy` manually on individual test source instead. This aligns
with how clang-tidy works and removes `mk-unity.pl` from the solution.
Also:
- mqttd: fix potentially uninitialized buffer by zero filling it.
```
tests/server/mqttd.c:484:41: error: The left operand of '<<' is a garbage value
[clang-analyzer-core.UndefinedBinaryOperatorResult,-warnings-as-errors]
484 | payload_len = (size_t)(buffer[10] << 8) | buffer[11];
| ^
[...]
tests/server/mqttd.c:606:45: error: The left operand of '<<' is a garbage value
[clang-analyzer-core.UndefinedBinaryOperatorResult,-warnings-as-errors]
606 | topiclen = (size_t)(buffer[1 + bytes] << 8) | buffer[2 + bytes];
| ^
```
- sockfilt: fix potential out-of-bound pointer:
```
tests/server/sockfilt.c:1128:33: error: The 2nd argument to 'send' is a buffer
with size 17010 but should be a buffer with size equal to or greater than
the value of the 3rd argument (which is 18446744073709551615)
[clang-analyzer-unix.StdCLibraryFunctions,-warnings-as-errors]
1128 | ssize_t bytes_written = swrite(sockfd, buffer, buffer_len);
| ^
```
- clang-tidy: suppress bogus `bzero()` warnings that happens
inside the notorious `FD_ZERO()` macros, on macOS.
Ref: https://github.com/curl/curl/pull/17680#issuecomment-2991730158Closes#17705
Also:
- pass `-D_GNU_SOURCE` via `COMPILE_DEFINITIONS`.
- make it explicit to pass these C flags to feature checks.
- update `_GNU_SOURCE` comment with `pipe2()`.
- enable `-pedantic-errors` picky option for GCC with CMake <3.23.
- drop redundant condition when stripping existing MSVC `/Wn` options.
CMake passes `CMAKE_C_FLAGS` to targets, feature checks and raw
`try_compile()` calls. With `COMPILE_OPTIONS`, this is limited to
targets, and we must explicitly pass them to feature checks. This
makes the build logic clearer, and offers more control. It also
reduces log noise by omitting these options from linker commands,
and from `CMAKE_C_FLAGS` dumps in feature checks.
Closes#17047
To save configuration time.
After this patch, for mingw-w64 and MSVC curl's CMake builds pre-fill
almost all type sizes without auto-detection. In most cases this leaves
3 type size auto-detections. Those depend on 64/32-bitness, and `time_t`
also depends on CRT and custom options. Old mingw-w64 versions require
some extra detections. We recommend v3.0 or newer to avoid them.
For Windows CE, this patch pre-fills all type sizes.
If this is causing any issue, please report it and disable pre-filling
with `-D_CURL_PREFILL=OFF` in the meantime.
Cherry-picked from #16394Closes#16464
- make `curl_dependency_option()` more generic.
- extend `CURL_BROTLI` and `CURL_ZSTD` options to accept
`AUTO` in addition to existing `ON` and `OFF`.
- change `CURL_BROTLI` and `CURL_ZSTD` option default
to `AUTO`. Was: `OFF`.
It brings cmake behavior closer to `./configure`.
Still different:
- `./configure` defaults to `off` which means to check default
locations. cmake checks more locations by default.
(Also tried `NO_CMAKE_PATH`, but then it checked less locations.)
- cmake returns both `brotlicommon` and `brotlidec` libs,
while `./configure` only returns the latter.
- ci: drop explicit cmake options, that are now unnecessary.
- GHA/configure-vs-cmake: make adjustments to make tests pass.
Closes#15431
Prefix (or suffix) curl-defined macro and function names with `curl`.
To avoid collisions with non-curl CMake and to make them recognizable
as curl-specific calls.
Closes#15498
It reduces the number of synonym variables in the code.
Makes it easier to grok and grep.
- replace `CURL_SOURCE_DIR`
with `PROJECT_SOURCE_DIR`.
- replace `CURL_BINARY_DIR`
with `PROJECT_BINARY_DIR` or `CMAKE_CURRENT_BINARY_DIR`.
- replace a single use of `CMAKE_BINARY_DIR`
with `PROJECT_BINARY_DIR`.
- replace `CMAKE_CURRENT_*_DIR`
with `PROJECT_*_DIR` where it makes the code more uniform.
- quote an argument (formatting).
Closes#15331
- limit `SIZEOF_SA_FAMILY_T` detection to non-Windows.
- make sure `sys/socket.h` exists before detecting `SIZEOF_SA_FAMILY_T`.
- limit `mach_absolute_time()` detection to `APPLE`. Drop from Windows
pre-cache.
- skip `HAVE_LIBSOCKET` detection for Windows, drop pre-cached value.
- drop redundant pre-cached `HAVE_LIBZ` for Windows.
- `curl_required_libpaths()`: stop accepting multiple arguments.
To prepare for `CMAKE_REQUIRED_LINK_DIRECTORIES` support.
Follow-up to 7bab201abe#15193
- GSS: fix recent rebase mistakes:
- fix variable name.
- do not add a header twice.
Follow-up to 91d451b488#15157
- GSS: quote a variable.
Closes#15271
- reduce `check_include_file_concat()` use to those headers that either
depend on a previously detected header, or another header or symbol
detection depend on it.
- replace `check_symbol_exists()` with `check_function_exists()` for
functions that are detected with `AC_CHECK_FUNCS()` in `./configure`.
This makes `setmode()` no longer be detected with MSYS, syncing
this with `./configure`. Instead `_setmode()` is used now also in
CMake MSYS builds. This is consistent with Cygwin builds also.
- add comment about which header/symbol detection depends on what
header. Based on `./configure` mainly.
- form `CURL_TEST_DEFINES` manually, and include only those macros which
are actually used in `CMake/CurlTests.c`.
- change `curl_internal_test()` to use `CMAKE_REQUIRED_DEFINITIONS`,
instead of `CMAKE_REQUIRED_FLAGS` to simplify the logic, and to allow
dropping the latter macro completely.
- drop `windows.h` from header and symbol checks.
- `./configure`: add comment about whether `netinet/in6.h`, `sys/un.h`
are indeed meant to be included for all detections. There is a chance
they were added there by accident.
Detection resuls were cross-checked between
436bbbe7ab (master) and
48ff4694e608ccfdedf7ce5bab2b96d6b2c23cda (this PR), for CI GHA Linux,
Linux HTTP/3, non-native, macOS and Windows jobs.
Closes#15164
Add comments saying when we want values set in feature check option
variables to apply to all feature checks, globally. These are currently:
`ws2_32` and `socket` libraries, and `-D_WIN32_WINNT=` macro.
Also use `list(APPEND ...)` for the libraries to avoid overwriting
potentially existing values.
Cherry-picked from #15157Closes#15253
Also:
- detect and add required system libraries for Rustls on macOS and
non-Windows.
- add Linux CMake jobs for the touched dependencies.
Caveats:
- MSH3 generates a broken `libmsh3.pc`, so needs manual config.
Upstream PR: https://github.com/nibanks/msh3/pull/225
- Rustls `.pc` file missing, so needs manual config.
An internal change worthy of mention is that we are using the lib path
and name information returned by `pkg-config` as-is. Meaning the libname
doesn't include the full path, like it's usual with native cmake
detection. The path comes separately and needs to be rolled separately.
For this we add it to targets via `link_directories()`. We also keep tab
of them in `CURL_LIBDIRS` and use that in `libcurl.pc`. Feature checks
also need to receive these paths. CMake doesn't offer
a `CMAKE_REQUIRED_*` variable for this purpose, only
a `CMAKE_REQUIRED_LINK_OPTIONS` accepting raw linker flags. Add a macro
to convert a list of paths to linker options to solve it. wolfSSL
requires this for now.
Closes#15193
- drop redundant internal variable `USE_ZLIB`, rely on `HAVE_LIBZ`.
- rename `optional_dependency()` -> `curl_dependency_option()`
Make `grep 'option('` hit this option. Namespaced.
It has a single use with `ZLIB`.
Closes#14918
- quote string literals.
In the hope it improves syntax-highlighting and readability.
- use lowercase, underscore-prefixed local var names.
As a hint for scope, to help readability.
- prefer `pkg_search_module` (over `pkg_check_modules`).
They are the same, but `pkg_search_module` stops searching
at the first hit.
- more `IN LISTS` in `foreach()`.
- OtherTests.cmake: clear `CMAKE_EXTRA_INCLUDE_FILES` after use.
- add `PROJECT_LABEL` for http/client and unit test targets.
- sync `Find*` module comments and formatting.
- drop a few local variables.
- drop bogus `CARES_LIBRARIES` from comment.
- unquote numeric literal.
Follow-up to acbc6b703f#14197Closes#14388
- tidy-up comments.
- use lowercase, underscore prefixed names for internal variables.
- use `IN LISTS` and `IN ITEMS` in `foreach()` loops.
- rename variable name `OUTPUT` to a more distinctive one.
- tidy-up `STREQUAL` syntax.
- delete commented code.
- indent/whitespace.
Closes#14197
Create ASCII version of manpage without nroff
- build src/tool_hugegelp.c from the ascii manpage
- move the the manpage and the ascii version build to docs/cmdline-opts
- remove all use of nroff from the build process
- should make the build entirely reproducible (by avoiding nroff)
- partly reverts 2620aa9 to build libcurl option man pages one by one
in cmake because the appveyor builds got all crazy until I did
The ASCII version of the manpage
- is built with gen.pl, just like the manpage is
- has a right-justified column making the appearance similar to the previous
version
- uses a 4-space indent per level (instead of the old version's 7)
- does not do hyphenation of words (which nroff does)
History
We first made the curl build use nroff for building the hugehelp file in
December 1998, for curl 5.2.
Closes#13047
- make more obvious which detection uses which prep steps.
- merge and streamline conditions.
- these should not alter detection results.
Also align log output messages from
`Macros.cmake` / `curl_internal_test` with rest of the build.
Closes#12551
The idea of `check_library_exists_concat()` is that it detects an
optional component and adds it to the list of libs that we also use in
subsequent component checks. This caused problems when detecting
components with unnecessary dependencies that were not yet built.
CMake offers the `CMAKE_REQUIRED_LIBRARIES` variable to set libs used
for component checks, which we already use in most cases. That left 4
uses of `check_library_exists_concat()`. Only one of these actually
needed the 'concat' feature (ldap/lber).
Delete this function and replace it with standard
`check_library_exists()` and manual management of our `CURL_LIBS`
list we use when linking build targets. And special logic to handle the
ldap/lber case.
(We have a similar function for headers: `check_include_file_concat()`.
It works, but problematic for performance reasons and because it hides
the actual headers required in `check_symbol_exists()` calls.)
Ref: #11537#11558Fixes#11285Fixes#11648Closes#12070
- 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
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
By differentiating between ON and AUTO it can make a missing zlib
library a hard error when CURL_ZLIB=ON is used.
Reviewed-by: Jakub Zakrzewski
Closes#6221Fixes#6173
Reported by the new script 'scripts/copyright.pl'. The script has a
regex whitelist for the files that don't need copyright headers.
Removed three (mostly usesless) README files from docs/
Closes#5141
Remove use of an old hack that takes advantage of the auto-dereference
behavior of the if() command to detect if a variable is defined. The
hack has the form:
if("${VAR} MATCHES "^${VAR}$")
where "${VAR}" is a macro argument reference. Use if(DEFINED) instead.
This also avoids warnings for CMake Policy CMP0054 in CMake 3.1.
Revert commit 2257deb502 (Cmake: Avoid cycle directory dependencies,
2014-08-22) and add a comment explaining the purpose of the original
code.
The check_library_exists_concat macro is intended to be called multiple
times on a sequence of possibly dependent libraries. Later libraries
may depend on earlier libraries when they are static. They cannot be
safely linked in reverse order on some platforms.
Signed-off-by: Brad King <brad.king@kitware.com>
Revert commit 1269df2e3b (Cmake: Don't check for all headers each
time, 2014-08-15) and add a comment explaining the purpose of the
original code.
The check_include_file_concat macro is intended to be called multiple
times on a sequence of possibly dependent headers. Later headers
may depend on earlier headers to provide declarations. They cannot
be safely included independently on some platforms.
For example, many POSIX APIs document including sys/types.h before some
other headers. Also on some OS X versions sys/socket.h must be included
before net/if.h or the check for the latter will fail.
Signed-off-by: Brad King <brad.king@kitware.com>
