The problem that clang_parseTranslationUnit has is that precompiled preamble is not reused the second time that is called code completion. Calculate the precompile preamble takes more than the 90% of these time so you should allow that the precompiled preamble was reused as soon as posible. By default it is reused the third time that … Read more
As others have pointed out in the comments, the “universal” constructor is not, in fact, supposed to always move from its argument. It’s supposed to move if the argument is really an rvalue, and copy if it’s an lvalue. The behaviour, you observe, which always moves, is a bug in libstdc++, which is now fixed … Read more
To get a list of all the predefined macros that the compiler uses, use this: clang -dM -E -x c /dev/null You can do the same for gcc.
The command clang is for C, and the command clang++ is for C++.
So far as I can tell, there is no command-line option to list which architectures a given clang binary supports, and even running strings on it doesn’t really help. Clang is essentially just a C to LLVM translator, and it’s LLVM itself that deals with the nitty-gritty of generating actual machine code, so it’s not … Read more
The IEEE 754-2008 Standard for Floating-Point Arithmetic and the ISO/IEC 10967 Language Independent Arithmetic (LIA) Standard, Part 1 answer why this is so. IEEE 754 ยง 6.3 The sign bit When either an input or result is NaN, this standard does not interpret the sign of a NaN. Note, however, that operations on bit strings … Read more
TL;DR By default, the current snapshot GCC 7 behaves inconsistently, while previous versions have default limit due to PARAM_MAX_COMPLETELY_PEEL_TIMES, which is 16. It can be overridden from command-line. The rationale of the limit is to prevent too aggressive loop unrolling, that can be a double-edged sword. GCC version <= 6.3.0 The relevant optimization option for … Read more
I found this related question. To sum it up, to find out about compiler optimization passes: llvm-as < /dev/null | opt -O3 -disable-output -debug-pass=Arguments As pointed out in Geoff Nixon‘s answer (+1), clang additionally runs some higher level optimizations, which we can retrieve with: echo ‘int;’ | clang -xc -O3 – -o /dev/null -\#\#\# Documentation … Read more
Unfortunately, there is no way to apply clang-format recursively. *.cpp will only match files in the current directory, not subdirectories. Even **/* doesn’t work. Luckily, there is a solution: grab all the file names with the find command and pipe them in. For example, if you want to format all .h and .cpp files in … Read more
This is often a caching problem. Usually it can be resolved by holding down the Option key and choosing Product > Clean Build Folder…