According to C++14 [expr.delete]/7: If the value of the operand of the delete-expression is not a null pointer value, then: [ …omitted… ] Otherwise, it is unspecified whether the deallocation function will be called. So both compilers do comply with the standard, because it’s unspecified whether operator delete is called for deletion of a null … Read more
I have not dug up the Java Language Specification, but I’d guess that it has to do with this difference: i++ < (Integer.MAX_VALUE – 1) never overflows. Once i reaches Integer.MAX_VALUE – 1 it is incremented to Integer.MAX_VALUE and then the loop terminates. i++ < Integer.MAX_VALUE contains an integer overflow. Once i reaches Integer.MAX_VALUE, it … Read more
The only time it’s useful to revert to assembly language is when the CPU instructions don’t have functional equivalents in C++ (e.g. single-instruction-multiple-data instructions, BCD or decimal arithmetic operations) AND the compiler doesn’t provide extra functions to wrap these operations (e.g. C++11 Standard has atomic operations including compare-and-swap, <cstdlib> has div/ldiv et al for getting … Read more
Here’s a simpler test case which points out that it’s a compiler bug: http://coliru.stacked-crooked.com/a/58b3f9b4edd8e373 #include <cstdint> int main() { uint32_t i = 0; uint32_t count = 1; while (1) { if( i < 5 ) count+=1; if (i == 0xFFFFFFFF) break; i++; } return count; // should return 6 } The assembly shows that it … Read more
Reading a variable (that was not declared as volatile) is not considered to be a “side effect” as specified by the C standard. So the program is free to read a location and then discard the result, as far as the C standard is concerned. This is very common. Suppose you request 1 byte of … Read more
The frequency impact depends on the width of the operation and the specific instruction used. There are three frequency levels, so-called licenses, from fastest to slowest: L0, L1 and L2. L0 is the “nominal” speed you’ll see written on the box: when the chip says “3.5 GHz turbo”, they are referring to the single-core L0 … Read more
The commented code affects how inlining is handled. If functionB gets longer/bigger (more bytecode instructions) it will not be inlined into functionA. So @J3D1 was able to use VMOptions to manually switch off inlining for functionB(): -XX:CompileCommand=dontinline,com.jd.benchmarking.StrangeBehaviour::functionB This appears to eliminate the delay with the shorter function. with the vm options you can display inlining … Read more
First off: recommended usage of CMake is to always specify CMAKE_BUILD_TYPE explicitly on the command line (if and only if using a single-configuration generator). Your use case deviates from this best practice, so treat this answer as “how you can do it,” not necessarily as “how you should do it.” To address the first issue, … Read more
On Monday your boss comes into your office and says “I need file A on my desk by Thursday and file B on my desk on Friday”. He first describes the things that he wants in file A and how he thinks you should do those and then describes the things he wants in file … Read more
Do they re-typecheck, in the example above K(M) and K(N)? Yes, they do. It’s not that bad, though. The typechecker knows that K(M) is an application of K to M. It knows what the type of K is, and that should be a function type. It knows what the type of M is, and it … Read more