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c++ source #1
Output
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Intel asm syntax
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Filters
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Debug intrinsics
Compiler
6502-c++ 11.1.0
ARM GCC 10.2.0
ARM GCC 10.3.0
ARM GCC 10.4.0
ARM GCC 10.5.0
ARM GCC 11.1.0
ARM GCC 11.2.0
ARM GCC 11.3.0
ARM GCC 11.4.0
ARM GCC 12.1.0
ARM GCC 12.2.0
ARM GCC 12.3.0
ARM GCC 13.1.0
ARM GCC 13.2.0
ARM GCC 13.2.0 (unknown-eabi)
ARM GCC 14.1.0
ARM GCC 4.5.4
ARM GCC 4.6.4
ARM GCC 5.4
ARM GCC 6.3.0
ARM GCC 6.4.0
ARM GCC 7.3.0
ARM GCC 7.5.0
ARM GCC 8.2.0
ARM GCC 8.5.0
ARM GCC 9.3.0
ARM GCC 9.4.0
ARM GCC 9.5.0
ARM GCC trunk
ARM gcc 10.2.1 (none)
ARM gcc 10.3.1 (2021.07 none)
ARM gcc 10.3.1 (2021.10 none)
ARM gcc 11.2.1 (none)
ARM gcc 5.4.1 (none)
ARM gcc 7.2.1 (none)
ARM gcc 8.2 (WinCE)
ARM gcc 8.3.1 (none)
ARM gcc 9.2.1 (none)
ARM msvc v19.0 (WINE)
ARM msvc v19.10 (WINE)
ARM msvc v19.14 (WINE)
ARM64 Morello gcc 10.1 Alpha 2
ARM64 gcc 10.2
ARM64 gcc 10.3
ARM64 gcc 10.4
ARM64 gcc 10.5.0
ARM64 gcc 11.1
ARM64 gcc 11.2
ARM64 gcc 11.3
ARM64 gcc 11.4.0
ARM64 gcc 12.1
ARM64 gcc 12.2.0
ARM64 gcc 12.3.0
ARM64 gcc 13.1.0
ARM64 gcc 13.2.0
ARM64 gcc 14.1.0
ARM64 gcc 4.9.4
ARM64 gcc 5.4
ARM64 gcc 5.5.0
ARM64 gcc 6.3
ARM64 gcc 6.4
ARM64 gcc 7.3
ARM64 gcc 7.5
ARM64 gcc 8.2
ARM64 gcc 8.5
ARM64 gcc 9.3
ARM64 gcc 9.4
ARM64 gcc 9.5
ARM64 gcc trunk
ARM64 msvc v19.14 (WINE)
AVR gcc 10.3.0
AVR gcc 11.1.0
AVR gcc 12.1.0
AVR gcc 12.2.0
AVR gcc 12.3.0
AVR gcc 13.1.0
AVR gcc 13.2.0
AVR gcc 14.1.0
AVR gcc 4.5.4
AVR gcc 4.6.4
AVR gcc 5.4.0
AVR gcc 9.2.0
AVR gcc 9.3.0
Arduino Mega (1.8.9)
Arduino Uno (1.8.9)
BPF clang (trunk)
BPF clang 13.0.0
BPF clang 14.0.0
BPF clang 15.0.0
BPF clang 16.0.0
BPF clang 17.0.1
BPF clang 18.1.0
BPF gcc 13.1.0
BPF gcc 13.2.0
BPF gcc trunk
EDG (experimental reflection)
EDG 6.5
EDG 6.5 (GNU mode gcc 13)
EDG 6.6
EDG 6.6 (GNU mode gcc 13)
FRC 2019
FRC 2020
FRC 2023
KVX ACB 4.1.0 (GCC 7.5.0)
KVX ACB 4.1.0-cd1 (GCC 7.5.0)
KVX ACB 4.10.0 (GCC 10.3.1)
KVX ACB 4.11.1 (GCC 10.3.1)
KVX ACB 4.12.0 (GCC 11.3.0)
KVX ACB 4.2.0 (GCC 7.5.0)
KVX ACB 4.3.0 (GCC 7.5.0)
KVX ACB 4.4.0 (GCC 7.5.0)
KVX ACB 4.6.0 (GCC 9.4.1)
KVX ACB 4.8.0 (GCC 9.4.1)
KVX ACB 4.9.0 (GCC 9.4.1)
KVX ACB 5.0.0 (GCC 12.2.1)
M68K gcc 13.1.0
M68K gcc 13.2.0
M68K gcc 14.1.0
M68k clang (trunk)
MRISC32 gcc (trunk)
MSP430 gcc 4.5.3
MSP430 gcc 5.3.0
MSP430 gcc 6.2.1
MinGW clang 14.0.3
MinGW clang 14.0.6
MinGW clang 15.0.7
MinGW clang 16.0.0
MinGW clang 16.0.2
MinGW gcc 11.3.0
MinGW gcc 12.1.0
MinGW gcc 12.2.0
MinGW gcc 13.1.0
RISC-V (32-bits) gcc (trunk)
RISC-V (32-bits) gcc 10.2.0
RISC-V (32-bits) gcc 10.3.0
RISC-V (32-bits) gcc 11.2.0
RISC-V (32-bits) gcc 11.3.0
RISC-V (32-bits) gcc 11.4.0
RISC-V (32-bits) gcc 12.1.0
RISC-V (32-bits) gcc 12.2.0
RISC-V (32-bits) gcc 12.3.0
RISC-V (32-bits) gcc 13.1.0
RISC-V (32-bits) gcc 13.2.0
RISC-V (32-bits) gcc 14.1.0
RISC-V (32-bits) gcc 8.2.0
RISC-V (32-bits) gcc 8.5.0
RISC-V (32-bits) gcc 9.4.0
RISC-V (64-bits) gcc (trunk)
RISC-V (64-bits) gcc 10.2.0
RISC-V (64-bits) gcc 10.3.0
RISC-V (64-bits) gcc 11.2.0
RISC-V (64-bits) gcc 11.3.0
RISC-V (64-bits) gcc 11.4.0
RISC-V (64-bits) gcc 12.1.0
RISC-V (64-bits) gcc 12.2.0
RISC-V (64-bits) gcc 12.3.0
RISC-V (64-bits) gcc 13.1.0
RISC-V (64-bits) gcc 13.2.0
RISC-V (64-bits) gcc 14.1.0
RISC-V (64-bits) gcc 8.2.0
RISC-V (64-bits) gcc 8.5.0
RISC-V (64-bits) gcc 9.4.0
RISC-V rv32gc clang (trunk)
RISC-V rv32gc clang 10.0.0
RISC-V rv32gc clang 10.0.1
RISC-V rv32gc clang 11.0.0
RISC-V rv32gc clang 11.0.1
RISC-V rv32gc clang 12.0.0
RISC-V rv32gc clang 12.0.1
RISC-V rv32gc clang 13.0.0
RISC-V rv32gc clang 13.0.1
RISC-V rv32gc clang 14.0.0
RISC-V rv32gc clang 15.0.0
RISC-V rv32gc clang 16.0.0
RISC-V rv32gc clang 17.0.1
RISC-V rv32gc clang 18.1.0
RISC-V rv32gc clang 9.0.0
RISC-V rv32gc clang 9.0.1
RISC-V rv64gc clang (trunk)
RISC-V rv64gc clang 10.0.0
RISC-V rv64gc clang 10.0.1
RISC-V rv64gc clang 11.0.0
RISC-V rv64gc clang 11.0.1
RISC-V rv64gc clang 12.0.0
RISC-V rv64gc clang 12.0.1
RISC-V rv64gc clang 13.0.0
RISC-V rv64gc clang 13.0.1
RISC-V rv64gc clang 14.0.0
RISC-V rv64gc clang 15.0.0
RISC-V rv64gc clang 16.0.0
RISC-V rv64gc clang 17.0.1
RISC-V rv64gc clang 18.1.0
RISC-V rv64gc clang 9.0.0
RISC-V rv64gc clang 9.0.1
Raspbian Buster
Raspbian Stretch
SPARC LEON gcc 12.2.0
SPARC LEON gcc 12.3.0
SPARC LEON gcc 13.1.0
SPARC LEON gcc 13.2.0
SPARC gcc 12.2.0
SPARC gcc 12.3.0
SPARC gcc 13.1.0
SPARC gcc 13.2.0
SPARC gcc 14.1.0
SPARC64 gcc 12.2.0
SPARC64 gcc 12.3.0
SPARC64 gcc 13.1.0
SPARC64 gcc 13.2.0
SPARC64 gcc 14.1.0
TI C6x gcc 12.2.0
TI C6x gcc 12.3.0
TI C6x gcc 13.1.0
TI C6x gcc 13.2.0
TI C6x gcc 14.1.0
TI CL430 21.6.1
VAX gcc NetBSDELF 10.4.0
VAX gcc NetBSDELF 10.5.0 (Nov 15 03:50:22 2023)
WebAssembly clang (trunk)
Xtensa ESP32 gcc 11.2.0 (2022r1)
Xtensa ESP32 gcc 12.2.0 (20230208)
Xtensa ESP32 gcc 8.2.0 (2019r2)
Xtensa ESP32 gcc 8.2.0 (2020r1)
Xtensa ESP32 gcc 8.2.0 (2020r2)
Xtensa ESP32 gcc 8.4.0 (2020r3)
Xtensa ESP32 gcc 8.4.0 (2021r1)
Xtensa ESP32 gcc 8.4.0 (2021r2)
Xtensa ESP32-S2 gcc 11.2.0 (2022r1)
Xtensa ESP32-S2 gcc 12.2.0 (20230208)
Xtensa ESP32-S2 gcc 8.2.0 (2019r2)
Xtensa ESP32-S2 gcc 8.2.0 (2020r1)
Xtensa ESP32-S2 gcc 8.2.0 (2020r2)
Xtensa ESP32-S2 gcc 8.4.0 (2020r3)
Xtensa ESP32-S2 gcc 8.4.0 (2021r1)
Xtensa ESP32-S2 gcc 8.4.0 (2021r2)
Xtensa ESP32-S3 gcc 11.2.0 (2022r1)
Xtensa ESP32-S3 gcc 12.2.0 (20230208)
Xtensa ESP32-S3 gcc 8.4.0 (2020r3)
Xtensa ESP32-S3 gcc 8.4.0 (2021r1)
Xtensa ESP32-S3 gcc 8.4.0 (2021r2)
arm64 msvc v19.28 VS16.9
arm64 msvc v19.29 VS16.10
arm64 msvc v19.29 VS16.11
arm64 msvc v19.30
arm64 msvc v19.31
arm64 msvc v19.32
arm64 msvc v19.33
arm64 msvc v19.34
arm64 msvc v19.35
arm64 msvc v19.36
arm64 msvc v19.37
arm64 msvc v19.38
arm64 msvc v19.latest
armv7-a clang (trunk)
armv7-a clang 10.0.0
armv7-a clang 10.0.1
armv7-a clang 11.0.0
armv7-a clang 11.0.1
armv7-a clang 12.0.0
armv7-a clang 12.0.1
armv7-a clang 13.0.0
armv7-a clang 13.0.1
armv7-a clang 14.0.0
armv7-a clang 15.0.0
armv7-a clang 16.0.0
armv7-a clang 17.0.1
armv7-a clang 18.1.0
armv7-a clang 9.0.0
armv7-a clang 9.0.1
armv8-a clang (all architectural features, trunk)
armv8-a clang (trunk)
armv8-a clang 10.0.0
armv8-a clang 10.0.1
armv8-a clang 11.0.0
armv8-a clang 11.0.1
armv8-a clang 12.0.0
armv8-a clang 13.0.0
armv8-a clang 14.0.0
armv8-a clang 15.0.0
armv8-a clang 16.0.0
armv8-a clang 17.0.1
armv8-a clang 18.1.0
armv8-a clang 9.0.0
armv8-a clang 9.0.1
ellcc 0.1.33
ellcc 0.1.34
ellcc 2017-07-16
hexagon-clang 16.0.5
llvm-mos atari2600-3e
llvm-mos atari2600-4k
llvm-mos atari2600-common
llvm-mos atari5200-supercart
llvm-mos atari8-cart-megacart
llvm-mos atari8-cart-std
llvm-mos atari8-cart-xegs
llvm-mos atari8-common
llvm-mos atari8-dos
llvm-mos c128
llvm-mos c64
llvm-mos commodore
llvm-mos cpm65
llvm-mos cx16
llvm-mos dodo
llvm-mos eater
llvm-mos mega65
llvm-mos nes
llvm-mos nes-action53
llvm-mos nes-cnrom
llvm-mos nes-gtrom
llvm-mos nes-mmc1
llvm-mos nes-mmc3
llvm-mos nes-nrom
llvm-mos nes-unrom
llvm-mos nes-unrom-512
llvm-mos osi-c1p
llvm-mos pce
llvm-mos pce-cd
llvm-mos pce-common
llvm-mos pet
llvm-mos rp6502
llvm-mos rpc8e
llvm-mos supervision
llvm-mos vic20
loongarch64 gcc 12.2.0
loongarch64 gcc 12.3.0
loongarch64 gcc 13.1.0
loongarch64 gcc 13.2.0
loongarch64 gcc 14.1.0
mips clang 13.0.0
mips clang 14.0.0
mips clang 15.0.0
mips clang 16.0.0
mips clang 17.0.1
mips clang 18.1.0
mips gcc 11.2.0
mips gcc 12.1.0
mips gcc 12.2.0
mips gcc 12.3.0
mips gcc 13.1.0
mips gcc 13.2.0
mips gcc 14.1.0
mips gcc 4.9.4
mips gcc 5.4
mips gcc 5.5.0
mips gcc 9.3.0 (codescape)
mips gcc 9.5.0
mips64 (el) gcc 12.1.0
mips64 (el) gcc 12.2.0
mips64 (el) gcc 12.3.0
mips64 (el) gcc 13.1.0
mips64 (el) gcc 13.2.0
mips64 (el) gcc 14.1.0
mips64 (el) gcc 4.9.4
mips64 (el) gcc 5.4.0
mips64 (el) gcc 5.5.0
mips64 (el) gcc 9.5.0
mips64 clang 13.0.0
mips64 clang 14.0.0
mips64 clang 15.0.0
mips64 clang 16.0.0
mips64 clang 17.0.1
mips64 clang 18.1.0
mips64 gcc 11.2.0
mips64 gcc 12.1.0
mips64 gcc 12.2.0
mips64 gcc 12.3.0
mips64 gcc 13.1.0
mips64 gcc 13.2.0
mips64 gcc 14.1.0
mips64 gcc 4.9.4
mips64 gcc 5.4.0
mips64 gcc 5.5.0
mips64 gcc 9.5.0
mips64el clang 13.0.0
mips64el clang 14.0.0
mips64el clang 15.0.0
mips64el clang 16.0.0
mips64el clang 17.0.1
mips64el clang 18.1.0
mipsel clang 13.0.0
mipsel clang 14.0.0
mipsel clang 15.0.0
mipsel clang 16.0.0
mipsel clang 17.0.1
mipsel clang 18.1.0
mipsel gcc 12.1.0
mipsel gcc 12.2.0
mipsel gcc 12.3.0
mipsel gcc 13.1.0
mipsel gcc 13.2.0
mipsel gcc 14.1.0
mipsel gcc 4.9.4
mipsel gcc 5.4.0
mipsel gcc 5.5.0
mipsel gcc 9.5.0
nanoMIPS gcc 6.3.0 (mtk)
power gcc 11.2.0
power gcc 12.1.0
power gcc 12.2.0
power gcc 12.3.0
power gcc 13.1.0
power gcc 13.2.0
power gcc 14.1.0
power gcc 4.8.5
power64 AT12.0 (gcc8)
power64 AT13.0 (gcc9)
power64 gcc 11.2.0
power64 gcc 12.1.0
power64 gcc 12.2.0
power64 gcc 12.3.0
power64 gcc 13.1.0
power64 gcc 13.2.0
power64 gcc 14.1.0
power64 gcc trunk
power64le AT12.0 (gcc8)
power64le AT13.0 (gcc9)
power64le clang (trunk)
power64le gcc 11.2.0
power64le gcc 12.1.0
power64le gcc 12.2.0
power64le gcc 12.3.0
power64le gcc 13.1.0
power64le gcc 13.2.0
power64le gcc 14.1.0
power64le gcc 6.3.0
power64le gcc trunk
powerpc64 clang (trunk)
s390x gcc 11.2.0
s390x gcc 12.1.0
s390x gcc 12.2.0
s390x gcc 12.3.0
s390x gcc 13.1.0
s390x gcc 13.2.0
s390x gcc 14.1.0
sh gcc 12.2.0
sh gcc 12.3.0
sh gcc 13.1.0
sh gcc 13.2.0
sh gcc 14.1.0
sh gcc 4.9.4
sh gcc 9.5.0
vast (trunk)
x64 msvc v19.0 (WINE)
x64 msvc v19.10 (WINE)
x64 msvc v19.14
x64 msvc v19.14 (WINE)
x64 msvc v19.15
x64 msvc v19.16
x64 msvc v19.20
x64 msvc v19.21
x64 msvc v19.22
x64 msvc v19.23
x64 msvc v19.24
x64 msvc v19.25
x64 msvc v19.26
x64 msvc v19.27
x64 msvc v19.28
x64 msvc v19.28 VS16.9
x64 msvc v19.29 VS16.10
x64 msvc v19.29 VS16.11
x64 msvc v19.30
x64 msvc v19.31
x64 msvc v19.32
x64 msvc v19.33
x64 msvc v19.34
x64 msvc v19.35
x64 msvc v19.36
x64 msvc v19.37
x64 msvc v19.38
x64 msvc v19.latest
x86 djgpp 4.9.4
x86 djgpp 5.5.0
x86 djgpp 6.4.0
x86 djgpp 7.2.0
x86 msvc v19.0 (WINE)
x86 msvc v19.10 (WINE)
x86 msvc v19.14
x86 msvc v19.14 (WINE)
x86 msvc v19.15
x86 msvc v19.16
x86 msvc v19.20
x86 msvc v19.21
x86 msvc v19.22
x86 msvc v19.23
x86 msvc v19.24
x86 msvc v19.25
x86 msvc v19.26
x86 msvc v19.27
x86 msvc v19.28
x86 msvc v19.28 VS16.9
x86 msvc v19.29 VS16.10
x86 msvc v19.29 VS16.11
x86 msvc v19.30
x86 msvc v19.31
x86 msvc v19.32
x86 msvc v19.33
x86 msvc v19.34
x86 msvc v19.35
x86 msvc v19.36
x86 msvc v19.37
x86 msvc v19.38
x86 msvc v19.latest
x86 nvc++ 22.11
x86 nvc++ 22.7
x86 nvc++ 22.9
x86 nvc++ 23.1
x86 nvc++ 23.11
x86 nvc++ 23.3
x86 nvc++ 23.5
x86 nvc++ 23.7
x86 nvc++ 23.9
x86 nvc++ 24.1
x86 nvc++ 24.3
x86-64 Zapcc 190308
x86-64 clang (amd-stg-open)
x86-64 clang (assertions trunk)
x86-64 clang (clangir)
x86-64 clang (experimental -Wlifetime)
x86-64 clang (experimental P1061)
x86-64 clang (experimental P1144)
x86-64 clang (experimental P1221)
x86-64 clang (experimental P2996)
x86-64 clang (experimental P3068)
x86-64 clang (experimental metaprogramming - P2632)
x86-64 clang (experimental pattern matching)
x86-64 clang (old concepts branch)
x86-64 clang (reflection)
x86-64 clang (resugar)
x86-64 clang (thephd.dev)
x86-64 clang (trunk)
x86-64 clang (variadic friends - P2893)
x86-64 clang (widberg)
x86-64 clang 10.0.0
x86-64 clang 10.0.0 (assertions)
x86-64 clang 10.0.1
x86-64 clang 11.0.0
x86-64 clang 11.0.0 (assertions)
x86-64 clang 11.0.1
x86-64 clang 12.0.0
x86-64 clang 12.0.0 (assertions)
x86-64 clang 12.0.1
x86-64 clang 13.0.0
x86-64 clang 13.0.0 (assertions)
x86-64 clang 13.0.1
x86-64 clang 14.0.0
x86-64 clang 14.0.0 (assertions)
x86-64 clang 15.0.0
x86-64 clang 15.0.0 (assertions)
x86-64 clang 16.0.0
x86-64 clang 16.0.0 (assertions)
x86-64 clang 17.0.1
x86-64 clang 17.0.1 (assertions)
x86-64 clang 18.1.0
x86-64 clang 18.1.0 (assertions)
x86-64 clang 2.6.0 (assertions)
x86-64 clang 2.7.0 (assertions)
x86-64 clang 2.8.0 (assertions)
x86-64 clang 2.9.0 (assertions)
x86-64 clang 3.0.0
x86-64 clang 3.0.0 (assertions)
x86-64 clang 3.1
x86-64 clang 3.1 (assertions)
x86-64 clang 3.2
x86-64 clang 3.2 (assertions)
x86-64 clang 3.3
x86-64 clang 3.3 (assertions)
x86-64 clang 3.4 (assertions)
x86-64 clang 3.4.1
x86-64 clang 3.5
x86-64 clang 3.5 (assertions)
x86-64 clang 3.5.1
x86-64 clang 3.5.2
x86-64 clang 3.6
x86-64 clang 3.6 (assertions)
x86-64 clang 3.7
x86-64 clang 3.7 (assertions)
x86-64 clang 3.7.1
x86-64 clang 3.8
x86-64 clang 3.8 (assertions)
x86-64 clang 3.8.1
x86-64 clang 3.9.0
x86-64 clang 3.9.0 (assertions)
x86-64 clang 3.9.1
x86-64 clang 4.0.0
x86-64 clang 4.0.0 (assertions)
x86-64 clang 4.0.1
x86-64 clang 5.0.0
x86-64 clang 5.0.0 (assertions)
x86-64 clang 5.0.1
x86-64 clang 5.0.2
x86-64 clang 6.0.0
x86-64 clang 6.0.0 (assertions)
x86-64 clang 6.0.1
x86-64 clang 7.0.0
x86-64 clang 7.0.0 (assertions)
x86-64 clang 7.0.1
x86-64 clang 7.1.0
x86-64 clang 8.0.0
x86-64 clang 8.0.0 (assertions)
x86-64 clang 8.0.1
x86-64 clang 9.0.0
x86-64 clang 9.0.0 (assertions)
x86-64 clang 9.0.1
x86-64 clang rocm-4.5.2
x86-64 clang rocm-5.0.2
x86-64 clang rocm-5.1.3
x86-64 clang rocm-5.2.3
x86-64 clang rocm-5.3.3
x86-64 clang rocm-5.7.0
x86-64 gcc (contract labels)
x86-64 gcc (contracts natural syntax)
x86-64 gcc (contracts)
x86-64 gcc (coroutines)
x86-64 gcc (modules)
x86-64 gcc (trunk)
x86-64 gcc 10.1
x86-64 gcc 10.2
x86-64 gcc 10.3
x86-64 gcc 10.4
x86-64 gcc 10.5
x86-64 gcc 11.1
x86-64 gcc 11.2
x86-64 gcc 11.3
x86-64 gcc 11.4
x86-64 gcc 12.1
x86-64 gcc 12.2
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template<typename TypeFrom,typename TypeTo> concept Inherit = requires(TypeTo *BasePointer,TypeFrom *SourcePointer) { BasePointer = SourcePointer; }; /// Testing type to be derived from 'TypeTo' to 'TypeFrom' with pointer casting (is able to test type to void conversion as well) template<typename To> struct HighLevelContainer { HighLevelContainer(HighLevelContainer const&) {} /// Copy constructor template<Inherit<To> From> /// Use 'Inherit' constraint HighLevelContainer(HighLevelContainer<From>) {} /// Conversion constructor with type argument derived from 'To' type : enabled }; struct Animal {}; /// Some Base class struct Cat; /// Forward declaration of 'Cat', defined later as derived from 'Animal' struct TestStruct /// Some class that need to be defined before 'ContextParasite' naturally { HighLevelContainer<Animal> test; TestStruct(HighLevelContainer<Animal>const g) : test{g} {} TestStruct(HighLevelContainer<Cat>const); // 'Cat' need to be forward declared here /// 'HighLevelContainer' doesn't need type argument to be defined }; struct ContextParasite /// Some class that need to be defined before 'Cat' { TestStruct member; // Use of 'TestStruct' defined ContextParasite(HighLevelContainer<Animal>const g) : member{g} {} /// Call the corresponding 'TestStruct' constructor ContextParasite(HighLevelContainer<Cat>const g) : member{g} {} // 'Cat' also need to be fowarded here /// Call the corresponding 'TestStruct' constructor /** !!! WARNING !!! Here start the troubles. These two constructors, when selecting the 'TestStruct' constructor overload, tries to evaluate the conversion constructor of the argument 'HighLevelContainer'. That evaluation picks the corresponding 'Inherit' concept and load its result. At that point, the concept result 'Inherit<Cat,Animal>' as well as 'Inherit<Animal,cat>' evaluate to "false". ( assigning 'Cat*' from 'Animal*' is invalid : unrelated types (!!! At that point !!!); assigning 'Animal*' from 'Cat*' is invalid : unrelated types (!!! At that point !!!); ) Then, 'Inherit<Cat,Cat>' and 'Inherit<Animal,Animal>' evaluate to "true", so matching type overloads are valid, but compiler may choose the non-template copy-constructor as a better alternative if such constructor is present (in this example it is, for coherency purpose with this bug report Note : the compiler in most cases is able to create implicit copy and move constructors) **/ }; struct Cat : Animal, TestStruct {}; /// Here we go, 'Cat' definition, using 'TestStruct' definition /** Cat may need to use 'ContextParasite' definition as well !! (and that's why we may need to define 'Cat' this late) I didn't put it like this however only for easy test purpose, but it compile as well and create troubles as well (see below). **/ TestStruct::TestStruct(HighLevelContainer<Cat>const g) : test{g} {} /// Define the 'TestStruct' constructor for 'HighLevelContainer<Cat>' // so it can use 'Cat' definition for conversion purpose (as 'Cat' is derived type from 'Animal') /** Here are the troubles, however this constructor definition is perfectly valid, and must trigger 'HighLevelContainer' conversion constructor : its evaluation fails. Why ? : It's simple, 'Inherit<Cat,Animal>' concept evaluate to "false", it's already well-known by the compiler. Though, in that context 'Inherit<Cat,Animal>' must evaluate to "true" : assigning 'Animal*' from 'Cat*' is well-defined here. 'Animal' is a base class of 'Cat'. Why does it still fail ? Despite 'HighLevelContainer' conversion constructor being a function __template__, the compiler doesn't evaluate it at the call site context, but instead load directly its "missing instantiation" from the last cached argument matching template instantiation attempt. There is the problem. It wasn't a problem before, as evaluation context was __only dependending on template arguments__. But now with C++20 : __It's also dependending on the concept and requires clause **context**__. So it __must__ be evaluated. You can easily put 'ContextParasite' definition after 'Cat' definition for testing purpose. Note : in that case 'HighLevelContainer' conversion corresponding overloads for its constructors would already be defined, and this is consistent, as it is implicitly declared after further functions's definitions (I mean : other 'HighLevelContainer' conversion constructor instantions are available then). Note : it can select non-template copy-constructor as a better overload, then it doesn't create ambiguous overload. **/ /* Side Note : It may be straight-forward to keep the first instantiated version of a template when further call encountered. But it's not straight-forward to keep a template non-instantiated when further call encoutered are valid. */
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