compiler-flags

In Objective-C I had a bunch of compiler flags set in Build Settings -> Other C Flags that were being used in the code. For instance: Flag => -DPortNumber = 1 And in code I was able to access it by @(PortNumber) This doesn't work in Swift, and I'm not able to find an answer. The -D flag to C compilers defines a preprocessor macro. There are no preprocessor macros in Swift. So if you're looking to do something like: // compile with -DPORT_NUMBER 31337 var port = PORT_NUMBER // error ... you can't. Swift is designed for source code to be syntactically complete before compilation. If you could

I've been tasked to work on a project that has some confusing attributes. The project is of the nature that it won't compile for the iPhone Simulator And the iPhone Device with the same compile settings. I think it has to do with needing to be specifically compiled for x86 or arm6/7 depending on the target platform. So the project's build settings, when viewed in Xcode's Build Settings view doesn't enable me to set specific compiler flags per specific files. However, the previous developer that worked on this project has somehow declared the line: CE7FEB5710F09234004DE356 /* MyFile.m in

Just learned here that -Wsequence-point comiplation flag will pop a warning when the code can invoke UB. I tried it on a statement like int x = 1; int y = x+ ++x; and it worked very nicely. Until now I have compiled with gcc or g++ only using -ansi -pedantic -Wall . Do you have any other helpful flags to make the code more safe and robust? gsamaras As alk summed up, use these flags: -pedantic -Wall -Wextra -Wconversion First, I think you don't want to use the -ansi flag, as suggested in Should I use "-ansi" or explicit "-std=..." as compiler flags? Secondly, -Wextra seems to be quite useful

What's the "DNS_BLOCK_ASSERTIONS" (C compiler flag)? The NS_BLOCK_ASSERTIONS macro (no "D") suppresses the checks performed by NSAssert. You supply it to the compiler using -DNS_BLOCK_ASSERTIONS (see the comments for an explanation of the "D"). 来源： https://stackoverflow.com/questions/2752574/whats-the-dns-block-assertions-c-compiler-flag

I am performing matrix operations using C. I would like to know what are the various compiler optimization flags to improve speed of execution of these matrix operations for double and int64 data - like Multiplication, Inverse, etc. I am not looking for hand optimized code, I just want to make the native code more faster using compiler flags and learn more about these flags. The flags that I have found so far which improve matrix code. -O3/O4 -funroll-loops -ffast-math First of all, I don't recommend using -ffast-math for the following reasons: It has been proved that the performance actually

HotSpot's tiered compilation uses the interpreter until a threshold of invocations (for methods) or iterations (for loops) triggers a client compilation with self-profiling. The client compilation is used until another threshold of invocations or iterations triggers a server compilation. Printing HotSpot's flags shows the following flag values with -XX:+TieredCompilation. intx CompileThreshold = 10000 {pd product} intx Tier2CompileThreshold = 0 {product} intx Tier3CompileThreshold = 2000 {product} intx Tier4CompileThreshold = 15000 {product} There are too many flags for just a client and

I'd want your input which gcc compiler flags to use when optimizing for Xeons? There's no 'xeon' in mtune or march so which is the closest match? ShuggyCoUk Xeon is a marketing term, as such it covers a long list of processors with very different internals. If you meant the newer Nehalem processors (Core i7) then this slide indicates that as of 4.3.1 gcc should be use -march=generic (though your own testing of your own app may find other settings that outperform this). The 4.3 series also added -msse4.2 if you wish to optimize that aspect of FP maths. Here is some discussion comparing tuning

When I compile my C++ program with g++ using the -Og option I see variables that are <optimized out> , and also the current line sometimes skips around. Is this behaviour expected at this optimization level, or do I have some problem? The man page of gcc says: -Og Optimize debugging experience. -Og enables optimizations that do not interfere with debugging. It should be the optimization level of choice for the standard edit-compile-debug cycle, offering a reasonable level of optimization while maintaining fast compilation and a good debugging experience. hence I did not expect this behaviour.