Several threads on stackoverflow (e.g. this one) discuss the different optimization levels (Onone, O, Ounchecked...) when compiling Swift applications.
However, those postings are related to the development on OSX. It seems that those optimizations can be set directly via Xcode or xcrun (xcrun swift -O3).
I'm wondering how to switch the different optimization levels when using the Swift compiler directly on Linux (Ubuntu 15.10). Currently, I'm building the application just by invoking swift build as it is shown in the docs, but I found no way no change the optimization level.
It is possible to provide the -O, -Onone, and -Ounchecked optimization flags to the Swift compiler, swiftc. However, it appears that there is currently no way to specify additional flags to swift build. See, for example, the following link, even though it is not directly related:
https://bugs.swift.org/browse/SR-397. The same bug report suggests that the team is actively working on adding this missing functionality.
One way that I found to work around the problem is to run swift build -v, find the first command that references -Onone, copy it and all the commands that follow it to a shell script, edit the script to use the desired optimization level instead of -Onone, and run the script. This should re-compile the Swift sources using the desired optimization level and rebuild the executable.
In my testing I found that a simple example involving sorting an array runs a couple of orders of magnitude faster if built using -O or -Ounchecked instead of -Onone.
Related
I'm trying to update an existing configuration we have we are cross compiling for a number of targets - the question specifically here is about Android. More specifically we are building code using cmake and the hunter package manager. However we are building ICU using a link that uses autoconf/configure, called from cmake. Not sure that is specifically important except that we have less control on the use of configure than is generally the case.
OK: we have a version that builds against an old NDK but I am updating and have hit a problem identified by https://android.googlesource.com/platform/ndk/+/master/docs/UnifiedHeaders.md: with NDK16 and later, the value of the sysroot parameter needs to vary between compilation and linkage. As it stands the configure script tries to build a small program conftest.c - the program fails to link. Manually I can compile the code in two stages using -c and then linking the subsequent .o, but that is not what configure is trying to do.
Now the reality is that when I build this code, I don't actually need to link the code - I am generating a library which is used elsewhere. However that is not currently the way that configure sees it.
I may look to redo the configuration script to just check that the code can be compiled when cross compiling. However I am curious to know if anybody has managed to handle this sort of thing by keeping the existing config files and just changing the parameters by which the scripts are called.
When r19 releases to stable this problem will go away on its own (https://github.com/android-ndk/ndk/issues/780), but since that's still in beta it's not a good solution just yet.
Prior to r19 (this isn't really unique to r16+, this has always been the case and it was just asymptomatic previously), autoconf builds should be done using a standalone toolchain.
You however should not use a standalone toolchain for CMake, so odds are something about your configuration will need to change until r19 is released. Depending on the effort involved, it may make sense to keep to r15 until r19 is available.
Let's say I want to use a specific Linux / POSIX feature, that is provided conditionally based on feature test macros. For example, the type cpu_set_t, the macro CPU_SET_ZERO, and the function sched_setaffinity.
Ideally I would just like to tell CMake that I need those, and it should figure out what extra feature test macros to set or fail with a nice error message if it can't be provided on the current system. Is that possible?
I am aware that I can lookup in the manpages and manually use add_definitions(-D_GNU_SOURCE), but that can become tedious once multiple functionalities that were introduced and deprecated in different versions of the POSIX standard are combined. In my experience, it can become difficult to maintain portability across different versions of the glibc implementation.
There are the CMake platform checks, but they only seem to help in checking. So I get the error during cmake rather than make, but I still have to figure out the right feature test macros manually.
cmake-compile-features seem to offer only features directly related to the compiler, not the library.
If you are just looking to determine whether a function or variable exists, you can use the CheckSymbolExists module. Likewise, there is CheckStructHasMember for structs (assuming there is a standard member you can check for). So:
include (CheckSymbolExists)
include (CheckStructHasMember)
CHECK_SYMBOL_EXISTS(CPU_SET_ZERO sched.h CPU_SET_ZERO_exists)
CHECK_SYMBOL_EXISTS(sched_setaffinity sched.h sched_setaffinity_exists)
CHECK_STRUCT_HAS_MEMBER(cpu_set_t <member?> sched.h cpu_set_t_exists)
It appears that cpu_set_t is an opaque type, so instead you can use the CheckCXXSourceCompiles module, which is a frontend for the try_compile command. It is a generic way to determine if any particular code compiles. try_compile is used extensively by 'base' CMake to determine features (try a search in the Modules directory!). Essentially, you pass it in a minimal source file, which should fail compilation if your feature is not present, and it reports back to your CMake script the result.
I'm having to build gnu make from source for reasons too complicated to explain here.
I noticed to build it I require the make command itself, in the traditional fashion:
./configure
make install
So what if I didn't have the make binary already? Where did the first ever make binary come from?
From the same place the first gcc binary came from.
The first make was created probably using a shell script to do the build. After that, make would "make" itself.
It's a notable achievement in systems development when the platform becomes "self-hosting". That is the platform can build itself.
Things like "make make" and "gcc gcc.c".
Many language writers will create their language in another language (say, C) and when they have moved it far enough along, they will use that original bootstrap compiler to write a new compiler in the original language. Finally, they discard the original.
Back in the day, a friend was working on a debugger for OS/2, notable for being a multi-tasking operating system at the time. And he would regale about the times when they would be debugging the debugger, and find a bug. So, they would debug the debugger debugging the debugger. It's a novel concept and goes to the heart of computing and abstraction.
Inevitably, it all boils back to when someone keyed in something through a hardwire key pad or some other switches to get an initial program loaded. Then they leveraged that program to do other work, and it all just grows from there.
Stuart Feldman, then at AT&T, wrote the source code for make around the time of 7th Edition UNIX™, and used manual compilation (or maybe a shell script) until make was working well enough to be used to build itself. You can find the UNIX Programmer's Manual for 7th Edition online, and in particular, the original paper describing the original version of make, dated August 1978.
make is just one convenience tool. It is still possible to invoke cc, ld, etc. manually or via other scripting tools.
If you're building GNU make, have a look at build.sh in the source tree after running configure:
# Shell script to build GNU Make in the absence of any `make' program.
# build.sh. Generated from build.sh.in by configure.
Compiling C programs is not the only way to produce an executable file. The first make executable (or more notably the C compiler itself) could for example be an assembly program, or it could be hand coded in machine code. It could also be cross compiled on a completely different system.
The essence of make is that it is a simplified way of running some commands.
To make the first make, the author had to manually act as make, and run gcc or whatever toolset was available, rather than having it run automatically.
I'm re-writing a build that produces a number of things (shared/static libraries, jars, executables, etc). The question came up whether there's a way to verify that the results are functionally equivalent without doing a full top-to-bottom test of the resulting software.
However, that is proving to be more difficult to do than I anticipated.
As an example, I expected that the md5 of two objects produced from the same source (sun studio C++ compiler) and command-line parameters would have the same md5 hash, but that isn't the case. I can build the file, rename it, build again, and they have different hashes.
With that said ... is there a way do a quick check to verify that two files produced from separate build architectures of the same source tree (eg, two shared objects) are functionally equivalent?
edit I am sorry, I neglected to mention this is for a debug build ... when debugging flags aren't used the binaries are identical, but they've been using debugging flags by default for so many years their stuff breaks when you remove the debugging flags (part of the reason I'm re-writing the build is to take that particular 'feature' out of the build so we can get some proper testing going)
Windows DLLs have a link timestamp (TimeDateStamp) as part of PE image.
Looking at linker options, I don't see an option to suppress that. So re-linking a DLL (or an EXE) will always produce a different binary.
You could write a tool to zero out these timestamps (always at a fixed offset from file start), and compare MD5s afterwards. But you'll likely discover lots of other differences as well. In particular, any program that uses __DATE__ or __TIME__ builtins will give you trouble.
We've had to work quite hard to achieve bit-identical rebuilds (using GNU toolchain). It's possible (at least for open-source tools, on Linux), but not easy (as you've discovered).
I forgot about this question; I'm revisiting so I can give the answer I came up with.
objcopy can be used to produce a new binary file in different formats. It's been a few years since I worked on this, so the specifics escape me, but here's what I recall:
objcopy can strip various things out (debug info, symbol information, etc), but even after stripping stuff out I was still seeing different hashes between objects.
In the end I found I could convert it from ELF to other formats. I ended up dumping it to another format (I think I chose SREC) that consistently provided the same MD5 for objects built at different times with identical source/flags.
I'm betting I could have done this a better way with objcopy (or perhaps another binutils tool), but it was good enough to satisfy our concerns.
I have a plugin project I've been developing for a few years where the plugin works with numerous combinations of [primary application version, 3rd party library version, 32-bit vs. 64-bit]. Is there a (clean) way to use autotools to create a single makefile that builds all versions of the plugin.
As far as I can tell from skimming through the autotools documentation, the closest approximation to what I'd like is to have N independent copies of the project, each with its own makefile. This seems a little suboptimal for testing and development as (a) I'd need to continually propagate code changes across all the different copies and (b) there is a lot of wasted space in duplicating the project so many times. Is there a better way?
EDIT:
I've been rolling my own solution for a while where I have a fancy makefile and some perl scripts to hunt down various 3rd party library versions, etc. As such, I'm open to other non-autotools solutions. For other build tools, I'd want them to be very easy for end users to install. The tools also need to be smart enough to hunt down various 3rd party libraries and headers without a huge amount of trouble. I'm mostly looking for a linux solution, but one that also works for Windows and/or the Mac would be a bonus.
If your question is:
Can I use the autotools on some machine A to create a single universal makefile that will work on all other machines?
then the answer is "No". The autotools do not even make a pretense at trying to do that. They are designed to contain portable code that will determine how to create a workable makefile on the target machine.
If your question is:
Can I use the autotools to configure software that needs to run on different machines, with different versions of the primary software which my plugin works with, plus various 3rd party libraries, not to mention 32-bit vs 64-bit issues?
then the answer is "Yes". The autotools are designed to be able to do that. Further, they work on Unix, Linux, MacOS X, BSD.
I have a program, SQLCMD (which pre-dates the Microsoft program of the same name by a decade and more), which works with the IBM Informix databases. It detects the version of the client software (called IBM Informix ESQL/C, part of the IBM Informix ClientSDK or CSDK) is installed, and whether it is 32-bit or 64-bit. It also detects which version of the software is installed, and adapts its functionality to what is available in the supporting product. It supports versions that have been released over a period of about 17 years. It is autoconfigured -- I had to write some autoconf macros for the Informix functionality, and for a couple of other gizmos (high resolution timing, presence of /dev/stdin etc). But it is doable.
On the other hand, I don't try and release a single makefile that fits all customer machines and environments; there are just too many possibilities for that to be sensible. But autotools takes care of the details for me (and my users). All they do is:
./configure
That's easier than working out how to edit the makefile. (Oh, for the first 10 years, the program was configured by hand. It was hard for people to do, even though I had pretty good defaults set up. That was why I moved to auto-configuration: it makes it much easier for people to install.)
Mr Fooz commented:
I want something in between. Customers will use multiple versions and bitnesses of the same base application on the same machine in my case. I'm not worried about cross-compilation such as building Windows binaries on Linux.
Do you need a separate build of your plugin for the 32-bit and 64-bit versions? (I'd assume yes - but you could surprise me.) So you need to provide a mechanism for the user to say
./configure --use-tppkg=/opt/tp/pkg32-1.0.3
(where tppkg is a code for your third-party package, and the location is specifiable by the user.) However, keep in mind usability: the fewer such options the user has to provide, the better; against that, do not hard code things that should be optional, such as install locations. By all means look in default locations - that's good. And default to the bittiness of the stuff you find. Maybe if you find both 32-bit and 64-bit versions, then you should build both -- that would require careful construction, though. You can always echo "Checking for TP-Package ..." and indicate what you found and where you found it. Then the installer can change the options. Make sure you document in './configure --help' what the options are; this is standard autotools practice.
Do not do anything interactive though; the configure script should run, reporting what it does. The Perl Configure script (note the capital letter - it is a wholly separate automatic configuration system) is one of the few intensively interactive configuration systems left (and that is probably mainly because of its heritage; if starting anew, it would most likely be non-interactive). Such systems are more of a nuisance to configure than the non-interactive ones.
Cross-compilation is tough. I've never needed to do it, thank goodness.
Mr Fooz also commented:
Thanks for the extra comments. I'm looking for something like:
./configure --use-tppkg=/opt/tp/pkg32-1.0.3 --use-tppkg=/opt/tp/pkg64-1.1.2
where it would create both the 32-bit and 64-bit targets in one makefile for the current platform.
Well, I'm sure it could be done; I'm not so sure that it is worth doing by comparison with two separate configuration runs with a complete rebuild in between. You'd probably want to use:
./configure --use-tppkg32=/opt/tp/pkg32-1.0.3 --use-tppkg64=/opt/tp/pkg64-1.1.2
This indicates the two separate directories. You'd have to decide how you're going to do the build, but presumably you'd have two sub-directories, such as 'obj-32' and 'obj-64' for storing the separate sets of object files. You'd also arrange your makefile along the lines of:
FLAGS_32 = ...32-bit compiler options...
FLAGS_64 = ...64-bit compiler options...
TPPKG32DIR = #TPPKG32DIR#
TPPKG64DIR = #TPPKG64DIR#
OBJ32DIR = obj-32
OBJ64DIR = obj-64
BUILD_32 = #BUILD_32#
BUILD_64 = #BUILD_64#
TPPKGDIR =
OBJDIR =
FLAGS =
all: ${BUILD_32} ${BUILD_64}
build_32:
${MAKE} TPPKGDIR=${TPPKG32DIR} OBJDIR=${OBJ32DIR} FLAGS=${FLAGS_32} build
build_64:
${MAKE} TPPKGDIR=${TPPKG64DIR} OBJDIR=${OBJ64DIR} FLAGS=${FLAGS_64} build
build: ${OBJDIR}/plugin.so
This assumes that the plugin would be a shared object. The idea here is that the autotool would detect the 32-bit or 64-bit installs for the Third Party Package, and then make substitutions. The BUILD_32 macro would be set to build_32 if the 32-bit package was required and left empty otherwise; the BUILD_64 macro would be handled similarly.
When the user runs 'make all', it will build the build_32 target first and the build_64 target next. To build the build_32 target, it will re-run make and configure the flags for a 32-bit build. Similarly, to build the build_64 target, it will re-run make and configure the flags for a 64-bit build. It is important that all the flags affected by 32-bit vs 64-bit builds are set on the recursive invocation of make, and that the rules for building objects and libraries are written carefully - for example, the rule for compiling source to object must be careful to place the object file in the correct object directory - using GCC, for example, you would specify (in a .c.o rule):
${CC} ${CFLAGS} -o ${OBJDIR}/$*.o -c $*.c
The macro CFLAGS would include the ${FLAGS} value which deals with the bits (for example, FLAGS_32 = -m32 and FLAGS_64 = -m64, and so when building the 32-bit version,FLAGS = -m32would be included in theCFLAGS` macro.
The residual issues in the autotools is working out how to determine the 32-bit and 64-bit flags. If the worst comes to the worst, you'll have to write macros for that yourself. However, I'd expect (without having researched it) that you can do it using standard facilities from the autotools suite.
Unless you create yourself a carefully (even ruthlessly) symmetric makefile, it won't work reliably.
As far as I know, you can't do that. However, are you stuck with autotools? Are neither CMake nor SCons an option?
We tried it and it doesn't work! So we use now SCons.
Some articles to this topic: 1 and 2
Edit:
Some small example why I love SCons:
env.ParseConfig('pkg-config --cflags --libs glib-2.0')
With this line of code you add GLib to the compile environment (env). And don't forget the User Guide which just great to learn SCons (you really don't have to know Python!). For the end user you could try SCons with PyInstaller or something like that.
And in comparison to make, you use Python, so a complete programming language! With this in mind you can do just everything (more or less).
Have you ever considered to use a single project with multiple build directories?
if your automake project is implemented in a proper way (i.e.: NOT like gcc)
the following is possible:
mkdir build1 build2 build3
cd build1
../configure $(YOUR_OPTIONS)
cd build2
../configure $(YOUR_OPTIONS2)
[...]
you are able to pass different configuration parameters like include directories and compilers (cross compilers i.e.).
you can then even run this in a single make call by running
make -C build1 -C build2 -C build3