MSBuild automatically includes the output objects of the CustomBuildStep
in the link command. If the objects are additionally added to the project,
they will be put twice on the linker command, which leads to LNK4042
warning.
MSBuild does not allow multiple CustomBuildStep elements. Therefore, all
input / output files and generator commands must be concatenated and put
into a single CustomBuildStep.
Noticed when trying to pass custom optimization flags, and hence setting
buildtype to plain, that warnings for different levels were not passed to
compiler.
This was a bit confusing since mesonconf still displayed "warning_level=3"
and -Werror was passed correctly due to "werror=true". So this change
aligns warning_level behavior with werror. That is, heed what is in
project() in meson.build but user can still override if necessary.
MSVC requires import libraries called foo.lib for linking to foo.dll, so
translate -lfoo to that. If foo.lib doesn't exist, linking will fail as
expected.
-Weverything is not a good match for behavior of other compilers at warning
level 3. Align flags with what Meson passes to GCC instead.
The warnings generated are often conflicting with what the user most
probably wants. E.g.:
* -Wc++98-compat does not make sense when building code that uses -std= to
set a later standard.
* -Wpadding warns when compiler pads classes and structs for better
performance, probably something the user wants.
These warnings, and maybe a couple of others, can of course be disabled by
Meson with -Wno-* but it is not future proof (other warnings that makes
sense to disable by default may be added which means Meson will probably
have to pass different flags depending on the Clang version).
It is also problematic to compile many system and library headers with
-Weverything. For instance:
* stdio.h and sigaction.h on Linux makes use of recursive macros
(-Wdisabled-macro-expansion).
* Many library headers make use of deprecated functionality (-Wdeprecated).
* Many library (e.g. GTK+ and Qt) headers trigger Clang's Doxygen warnings
(-Wdocumentation-unknown-command and -Wdocumentation).
There are a couple of more warnings that need to be disabled when building
files that use GTK+ and Qt. GTest is also problematic.
Maybe it would make sense to add a higher level, where -Weverything would
be passed to Clang, that aligns with the original intent of -Weverything.
See http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20121029/067071.html .
GCC does not have a similar flag though. I do not know about other
compilers (MSVC etc).
This is very useful to prevent compiler noise about invalid cflags; particularly
for the -mms-bitfields cflag which most libraries send to the mingw-gcc
compiler. More can be added later.
Instead of checking if we're on Windows and not even trying, try to symlink and
if that fails due to insufficient privileges, then just continue. This allows
people who know what they're doing to allow users other than Administrators to
make symlinks on Windows, or allows them to just run Meson as an Administrator.
On Windows, the advantages of PIC are provided by the runtime DLL loader. /LD is
also only valid as an argument to cl.exe, and the linker link.exe just barfs
when it sees it.
The code assumes that the compiler is the same as the linker which caused this
problem to occur.
Jussi Pakkanen