Wednesday, March 21, 2018

Digest for comp.lang.c++@googlegroups.com - 24 updates in 3 topics

"Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid>: Mar 20 01:24AM -0700

I have always used my custom asm for this, but I noticed a while ago
that C++11 can use Double-Width Compare-and-Swap (DWCAS) via a struct
the size of two pointers for atomic operations. Out of interest, I have
constructed the following program that works on MSVC 14.0.25424.00
Update 3. However, on GCC 6.3.0, I am getting the following errors:
____________________________
||=== Build: Debug in ct_experiment (compiler: GNU GCC Compiler) ===|
obj\Debug\main.o||In function `std::atomic<ct_dwcas>::is_lock_free()
const':|
C:\msys64\mingw64\include\c++\6.3.0\atomic|212|undefined reference to
`__atomic_is_lock_free'|
obj\Debug\main.o||In function
`std::atomic<ct_dwcas>::load(std::memory_order) const':|
C:\msys64\mingw64\include\c++\6.3.0\atomic|235|undefined reference to
`__atomic_load_16'|
obj\Debug\main.o||In function
`std::atomic<ct_dwcas>::compare_exchange_weak(ct_dwcas&, ct_dwcas,
std::memory_order, std::memory_order)':|
C:\msys64\mingw64\include\c++\6.3.0\atomic|268|undefined reference to
`__atomic_compare_exchange_16'|
||error: ld returned 1 exit status|
||=== Build failed: 4 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|
____________________________
 
Here is the code:
____________________________
#if defined (_MSC_VER)
# define _ENABLE_ATOMIC_ALIGNMENT_FIX // for dwcas
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