我们都知道，如果在一个函数调用另一个函数，假设是 main 函数调用 fun 函数，这个 fun 函数返回一个临时类类型变量，那么这个时候编译器就会在 main 函数申请一个空间并生成一个临时对象，通过拷贝构造函数将 fun 返回的临时变量的值拷贝到这个临时对象。我们看如下的代码：
#include <iostream> #include <cstring> using namespace std; class Matrix { public: explicit Matrix(double d = 1.0) { cout << "Matrix::Matrix()" << endl; for(int i = 0; i < 10; i++) for(int j = 0; j < 10; j++) m[i][j] = d; } Matrix(const Matrix& mt) { cout << "Matrix::Matrix(const Matrix&)" << endl; memcpy(this, &mt, sizeof(Matrix)); } Matrix& operator=(const Matrix& mt) { if(this == &mt) return *this; cout << "Matrix::operator=(const Matrix&)" << endl; memcpy(this, &mt, sizeof(Matrix)); return *this; } friend const Matrix operator+(const Matrix&, const Matrix&); //... private: double m[10][10]; }; const Matrix operator+(const Matrix& arg1, const Matrix& arg2) { Matrix sum; for(int i = 0; i < 10; i++) for(int j = 0; j < 10; j++) sum.m[i][j] = arg1.m[i][j] + arg2.m[i][j]; return sum; } int main() { Matrix a(2.0), b(3.0); Matrix c = (a + b); return 0; }
按照我们的预期，输出结果应该是这样的：
这也正是 vs2012 的执行结果，但是在 GCC4.2.1 中的执行结果却是这样的：
这样看来，在构造 c 的时候根本就没有调用拷贝构造函数，同时也没用调用赋值操作符和构造函数。这样就会有一个问题，c 到底是怎么构造的？我们把代码改成这样：
#include <iostream> #include <cstring> using namespace std; class Matrix { public: explicit Matrix(double d = 1.0) { cout << "Matrix::Matrix()" << endl; for(int i = 0; i < 10; i++) for(int j = 0; j < 10; j++) m[i][j] = d; } Matrix(const Matrix& mt) { cout << "Matrix::Matrix(const Matrix&)" << endl; memcpy(this, &mt, sizeof(Matrix)); } Matrix& operator=(const Matrix& mt) { if(this == &mt) return *this; cout << "Matrix::operator=(const Matrix&)" << endl; memcpy(this, &mt, sizeof(Matrix)); return *this; } friend const Matrix operator+(const Matrix&, const Matrix&); //... private: double m[10][10]; }; const Matrix operator+(const Matrix& arg1, const Matrix& arg2) { Matrix sum; for(int i = 0; i < 10; i++) for(int j = 0; j < 10; j++) sum.m[i][j] = arg1.m[i][j] + arg2.m[i][j]; cout << "Address of sum: " << &sum << endl; return sum; } int main() { Matrix a(2.0), b(3.0); Matrix c = (a + b); cout << "Address of c: " << &c << endl; return 0; }
其实就是把 sum 和 c 的地址打了出来，我们会发现在 gcc 的结果如下：
从这里可以看出，gcc 编译器对 c 的初始化做了优化，它没有再调用拷贝构造函数来构造 c，而是直接让 c 指向了 + 函数里的临时变量。当然这里也让 sum 的空间所有权交给了 main 作用域的 c, 否则在推出 sum 的时候 sum 的空间就应该被释放了。
这只是我从其执行结果推测的结果，而 gcc 产生的目标文件的汇编代码简直没法看，所以没有研究其汇编代码来验证我的想法，有人看得懂 gcc 的汇编代码的看完结果望告知！下面是代码的gcc汇编代码：
.section __TEXT,__text,regular,pure_instructions .globl __ZplRK6MatrixS1_ .align 4, 0x90 __ZplRK6MatrixS1_: ## @_ZplRK6MatrixS1_ .cfi_startproc ## BB#0: pushq %rbp Ltmp2: .cfi_def_cfa_offset 16 Ltmp3: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp4: .cfi_def_cfa_register %rbp subq $64, %rsp movq %rdi, %rax movabsq $1, %rcx cvtsi2sdq %rcx, %xmm0 movq %rsi, -24(%rbp) movq %rdx, -32(%rbp) movq %rdi, -48(%rbp) ## 8-byte Spill movq %rax, -56(%rbp) ## 8-byte Spill callq __ZN6MatrixC1Ed movl $0, -36(%rbp) LBB0_1: ## =>This Loop Header: Depth=1 ## Child Loop BB0_3 Depth 2 cmpl $10, -36(%rbp) jge LBB0_8 ## BB#2: ## in Loop: Header=BB0_1 Depth=1 movl $0, -40(%rbp) LBB0_3: ## Parent Loop BB0_1 Depth=1 ## => This Inner Loop Header: Depth=2 cmpl $10, -40(%rbp) jge LBB0_6 ## BB#4: ## in Loop: Header=BB0_3 Depth=2 movslq -40(%rbp), %rax movslq -36(%rbp), %rcx movq -24(%rbp), %rdx imulq $80, %rcx, %rcx addq %rcx, %rdx movsd (%rdx,%rax,8), %xmm0 movslq -40(%rbp), %rax movslq -36(%rbp), %rcx movq -32(%rbp), %rdx imulq $80, %rcx, %rcx addq %rcx, %rdx addsd (%rdx,%rax,8), %xmm0 movslq -40(%rbp), %rax movslq -36(%rbp), %rcx imulq $80, %rcx, %rcx movq -48(%rbp), %rdx ## 8-byte Reload addq %rcx, %rdx movsd %xmm0, (%rdx,%rax,8) ## BB#5: ## in Loop: Header=BB0_3 Depth=2 movl -40(%rbp), %eax addl $1, %eax movl %eax, -40(%rbp) jmp LBB0_3 LBB0_6: ## in Loop: Header=BB0_1 Depth=1 jmp LBB0_7 LBB0_7: ## in Loop: Header=BB0_1 Depth=1 movl -36(%rbp), %eax addl $1, %eax movl %eax, -36(%rbp) jmp LBB0_1 LBB0_8: movq __ZNSt3__14coutE@GOTPCREL(%rip), %rdi leaq L_.str(%rip), %rsi callq __ZNSt3__1lsINS_11char_traitsIcEEEERNS_13basic_ostreamIcT_EES6_PKc movq -48(%rbp), %rsi ## 8-byte Reload movq %rax, %rdi callq __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPKv leaq __ZNSt3__14endlIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_(%rip), %rsi movq %rax, -8(%rbp) movq %rsi, -16(%rbp) movq -8(%rbp), %rdi callq *-16(%rbp) movq -56(%rbp), %rsi ## 8-byte Reload movq %rax, -64(%rbp) ## 8-byte Spill movq %rsi, %rax addq $64, %rsp popq %rbp retq .cfi_endproc .section __TEXT,__textcoal_nt,coalesced,pure_instructions .globl __ZN6MatrixC1Ed .weak_def_can_be_hidden __ZN6MatrixC1Ed .align 4, 0x90 __ZN6MatrixC1Ed: ## @_ZN6MatrixC1Ed .cfi_startproc ## BB#0: pushq %rbp Ltmp7: .cfi_def_cfa_offset 16 Ltmp8: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp9: .cfi_def_cfa_register %rbp subq $16, %rsp movq %rdi, -8(%rbp) movsd %xmm0, -16(%rbp) movq -8(%rbp), %rdi movsd -16(%rbp), %xmm0 callq __ZN6MatrixC2Ed addq $16, %rsp popq %rbp retq .cfi_endproc .globl __ZNSt3__1lsINS_11char_traitsIcEEEERNS_13basic_ostreamIcT_EES6_PKc .weak_def_can_be_hidden __ZNSt3__1lsINS_11char_traitsIcEEEERNS_13basic_ostreamIcT_EES6_PKc .align 4, 0x90 __ZNSt3__1lsINS_11char_traitsIcEEEERNS_13basic_ostreamIcT_EES6_PKc: ## @_ZNSt3__1lsINS_11char_traitsIcEEEERNS_13basic_ostreamIcT_EES6_PKc .cfi_startproc ## BB#0: pushq %rbp Ltmp12: .cfi_def_cfa_offset 16 Ltmp13: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp14: .cfi_def_cfa_register %rbp subq $48, %rsp movq %rdi, -16(%rbp) movq %rsi, -24(%rbp) movq -16(%rbp), %rdi movq -24(%rbp), %rsi movq -24(%rbp), %rax movq %rax, -8(%rbp) movq -8(%rbp), %rax movq %rdi, -32(%rbp) ## 8-byte Spill movq %rax, %rdi movq %rsi, -40(%rbp) ## 8-byte Spill callq _strlen movq -32(%rbp), %rdi ## 8-byte Reload movq -40(%rbp), %rsi ## 8-byte Reload movq %rax, %rdx callq __ZNSt3__124__put_character_sequenceIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_PKS4_m addq $48, %rsp popq %rbp retq .cfi_endproc .private_extern __ZNSt3__14endlIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_ .globl __ZNSt3__14endlIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_ .weak_definition __ZNSt3__14endlIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_ .align 4, 0x90 __ZNSt3__14endlIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_: ## @_ZNSt3__14endlIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_ .cfi_startproc .cfi_personality 155, ___gxx_personality_v0 Leh_func_begin3: .cfi_lsda 16, Lexception3 ## BB#0: pushq %rbp Ltmp25: .cfi_def_cfa_offset 16 Ltmp26: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp27: .cfi_def_cfa_register %rbp subq $144, %rsp movq %rdi, -72(%rbp) movq %rdi, %rax movq (%rdi), %rcx movq -24(%rcx), %rcx addq %rcx, %rdi movq %rdi, -32(%rbp) movb $10, -33(%rbp) movq -32(%rbp), %rsi leaq -48(%rbp), %rcx movq %rcx, %rdi movq %rax, -80(%rbp) ## 8-byte Spill movq %rcx, -88(%rbp) ## 8-byte Spill callq __ZNKSt3__18ios_base6getlocEv movq -88(%rbp), %rax ## 8-byte Reload movq %rax, -24(%rbp) Ltmp15: movq __ZNSt3__15ctypeIcE2idE@GOTPCREL(%rip), %rsi movq %rax, %rdi callq __ZNKSt3__16locale9use_facetERNS0_2idE Ltmp16: movq %rax, -96(%rbp) ## 8-byte Spill jmp LBB3_1 LBB3_1: ## %_ZNSt3__19use_facetINS_5ctypeIcEEEERKT_RKNS_6localeE.exit.i movb -33(%rbp), %al movq -96(%rbp), %rcx ## 8-byte Reload movq %rcx, -8(%rbp) movb %al, -9(%rbp) movq -8(%rbp), %rdx movq (%rdx), %rsi movq 56(%rsi), %rsi movsbl -9(%rbp), %edi Ltmp17: movl %edi, -100(%rbp) ## 4-byte Spill movq %rdx, %rdi movl -100(%rbp), %r8d ## 4-byte Reload movq %rsi, -112(%rbp) ## 8-byte Spill movl %r8d, %esi movq -112(%rbp), %rdx ## 8-byte Reload callq *%rdx Ltmp18: movb %al, -113(%rbp) ## 1-byte Spill jmp LBB3_5 LBB3_2: Ltmp19: movl %edx, %ecx movq %rax, -56(%rbp) movl %ecx, -60(%rbp) Ltmp20: leaq -48(%rbp), %rdi callq __ZNSt3__16localeD1Ev Ltmp21: jmp LBB3_3 LBB3_3: movq -56(%rbp), %rdi callq __Unwind_Resume LBB3_4: Ltmp22: movl %edx, %ecx movq %rax, %rdi movl %ecx, -120(%rbp) ## 4-byte Spill callq ___clang_call_terminate LBB3_5: ## %_ZNKSt3__19basic_iosIcNS_11char_traitsIcEEE5widenEc.exit leaq -48(%rbp), %rdi callq __ZNSt3__16localeD1Ev movq -80(%rbp), %rdi ## 8-byte Reload movb -113(%rbp), %al ## 1-byte Reload movsbl %al, %esi callq __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE3putEc movq -72(%rbp), %rdi movq %rax, -128(%rbp) ## 8-byte Spill callq __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE5flushEv movq -72(%rbp), %rdi movq %rax, -136(%rbp) ## 8-byte Spill movq %rdi, %rax addq $144, %rsp popq %rbp retq .cfi_endproc Leh_func_end3: .section __TEXT,__gcc_except_tab .align 2 GCC_except_table3: Lexception3: .byte 255 ## @LPStart Encoding = omit .byte 155 ## @TType Encoding = indirect pcrel sdata4 .asciz "274" ## @TType base offset .byte 3 ## Call site Encoding = udata4 .byte 52 ## Call site table length Lset0 = Leh_func_begin3-Leh_func_begin3 ## >> Call Site 1 << .long Lset0 Lset1 = Ltmp15-Leh_func_begin3 ## Call between Leh_func_begin3 and Ltmp15 .long Lset1 .long 0 ## has no landing pad .byte 0 ## On action: cleanup Lset2 = Ltmp15-Leh_func_begin3 ## >> Call Site 2 << .long Lset2 Lset3 = Ltmp18-Ltmp15 ## Call between Ltmp15 and Ltmp18 .long Lset3 Lset4 = Ltmp19-Leh_func_begin3 ## jumps to Ltmp19 .long Lset4 .byte 0 ## On action: cleanup Lset5 = Ltmp20-Leh_func_begin3 ## >> Call Site 3 << .long Lset5 Lset6 = Ltmp21-Ltmp20 ## Call between Ltmp20 and Ltmp21 .long Lset6 Lset7 = Ltmp22-Leh_func_begin3 ## jumps to Ltmp22 .long Lset7 .byte 1 ## On action: 1 Lset8 = Ltmp21-Leh_func_begin3 ## >> Call Site 4 << .long Lset8 Lset9 = Leh_func_end3-Ltmp21 ## Call between Ltmp21 and Leh_func_end3 .long Lset9 .long 0 ## has no landing pad .byte 0 ## On action: cleanup .byte 1 ## >> Action Record 1 << ## Catch TypeInfo 1 .byte 0 ## No further actions ## >> Catch TypeInfos << .long 0 ## TypeInfo 1 .align 2 .section __TEXT,__text,regular,pure_instructions .globl _main .align 4, 0x90 _main: ## @main .cfi_startproc ## BB#0: pushq %rbp Ltmp30: .cfi_def_cfa_offset 16 Ltmp31: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp32: .cfi_def_cfa_register %rbp subq $2448, %rsp ## imm = 0x990 leaq -824(%rbp), %rdi movabsq $2, %rax cvtsi2sdq %rax, %xmm0 movl $0, -20(%rbp) callq __ZN6MatrixC1Ed leaq -1624(%rbp), %rdi movabsq $3, %rax cvtsi2sdq %rax, %xmm0 callq __ZN6MatrixC1Ed leaq -2424(%rbp), %rdi leaq -824(%rbp), %rsi leaq -1624(%rbp), %rdx callq __ZplRK6MatrixS1_ movq __ZNSt3__14coutE@GOTPCREL(%rip), %rdi leaq L_.str1(%rip), %rsi callq __ZNSt3__1lsINS_11char_traitsIcEEEERNS_13basic_ostreamIcT_EES6_PKc leaq -2424(%rbp), %rdx movq %rax, %rdi movq %rdx, %rsi callq __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEElsEPKv movl $0, %ecx leaq __ZNSt3__14endlIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_(%rip), %rdx movq %rax, -8(%rbp) movq %rdx, -16(%rbp) movq -8(%rbp), %rdi movl %ecx, -2428(%rbp) ## 4-byte Spill callq *-16(%rbp) movl -2428(%rbp), %ecx ## 4-byte Reload movq %rax, -2440(%rbp) ## 8-byte Spill movl %ecx, %eax addq $2448, %rsp ## imm = 0x990 popq %rbp retq .cfi_endproc .section __TEXT,__textcoal_nt,coalesced,pure_instructions .private_extern ___clang_call_terminate .globl ___clang_call_terminate .weak_def_can_be_hidden ___clang_call_terminate .align 4, 0x90 ___clang_call_terminate: ## @__clang_call_terminate ## BB#0: pushq %rbp movq %rsp, %rbp subq $16, %rsp callq ___cxa_begin_catch movq %rax, -8(%rbp) ## 8-byte Spill callq __ZSt9terminatev .globl __ZNSt3__124__put_character_sequenceIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_PKS4_m .weak_def_can_be_hidden __ZNSt3__124__put_character_sequenceIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_PKS4_m .align 4, 0x90 __ZNSt3__124__put_character_sequenceIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_PKS4_m: ## @_ZNSt3__124__put_character_sequenceIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_PKS4_m .cfi_startproc .cfi_personality 155, ___gxx_personality_v0 Leh_func_begin6: .cfi_lsda 16, Lexception6 ## BB#0: pushq %rbp Ltmp65: .cfi_def_cfa_offset 16 Ltmp66: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp67: .cfi_def_cfa_register %rbp subq $416, %rsp ## imm = 0x1A0 movq %rdi, -208(%rbp) movq %rsi, -216(%rbp) movq %rdx, -224(%rbp) movq -208(%rbp), %rsi Ltmp33: leaq -240(%rbp), %rdi callq __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE6sentryC1ERS3_ Ltmp34: jmp LBB6_1 LBB6_1: leaq -240(%rbp), %rax movq %rax, -200(%rbp) movq -200(%rbp), %rax movb (%rax), %cl movb %cl, -273(%rbp) ## 1-byte Spill ## BB#2: movb -273(%rbp), %al ## 1-byte Reload testb $1, %al jne LBB6_3 jmp LBB6_26 LBB6_3: leaq -264(%rbp), %rax movq -208(%rbp), %rcx movq %rax, -184(%rbp) movq %rcx, -192(%rbp) movq -184(%rbp), %rax movq -192(%rbp), %rcx movq %rax, -152(%rbp) movq %rcx, -160(%rbp) movq -152(%rbp), %rax movq -160(%rbp), %rcx movq (%rcx), %rdx movq -24(%rdx), %rdx addq %rdx, %rcx movq %rcx, -144(%rbp) movq -144(%rbp), %rcx movq %rcx, -136(%rbp) movq -136(%rbp), %rcx movq 40(%rcx), %rcx movq %rcx, (%rax) movq -216(%rbp), %rsi movq -208(%rbp), %rax movq (%rax), %rcx movq -24(%rcx), %rcx addq %rcx, %rax movq %rax, -96(%rbp) movq -96(%rbp), %rax movl 8(%rax), %edi movq %rsi, -288(%rbp) ## 8-byte Spill movl %edi, -292(%rbp) ## 4-byte Spill ## BB#4: movl -292(%rbp), %eax ## 4-byte Reload andl $176, %eax cmpl $32, %eax jne LBB6_6 ## BB#5: movq -216(%rbp), %rax addq -224(%rbp), %rax movq %rax, -304(%rbp) ## 8-byte Spill jmp LBB6_7 LBB6_6: movq -216(%rbp), %rax movq %rax, -304(%rbp) ## 8-byte Spill LBB6_7: movq -304(%rbp), %rax ## 8-byte Reload movq -216(%rbp), %rcx addq -224(%rbp), %rcx movq -208(%rbp), %rdx movq (%rdx), %rsi movq -24(%rsi), %rsi addq %rsi, %rdx movq -208(%rbp), %rsi movq (%rsi), %rdi movq -24(%rdi), %rdi addq %rdi, %rsi movq %rsi, -80(%rbp) movq -80(%rbp), %rsi movl 144(%rsi), %r8d movl $-1, -4(%rbp) movl %r8d, -8(%rbp) movl -4(%rbp), %r8d cmpl -8(%rbp), %r8d movq %rax, -312(%rbp) ## 8-byte Spill movq %rcx, -320(%rbp) ## 8-byte Spill movq %rdx, -328(%rbp) ## 8-byte Spill movq %rsi, -336(%rbp) ## 8-byte Spill jne LBB6_16 ## BB#8: movq -336(%rbp), %rax ## 8-byte Reload movq %rax, -40(%rbp) movb $32, -41(%rbp) movq -40(%rbp), %rsi Ltmp35: leaq -56(%rbp), %rdi callq __ZNKSt3__18ios_base6getlocEv Ltmp36: jmp LBB6_9 LBB6_9: ## %.noexc leaq -56(%rbp), %rax movq %rax, -32(%rbp) Ltmp37: movq __ZNSt3__15ctypeIcE2idE@GOTPCREL(%rip), %rsi movq %rax, %rdi callq __ZNKSt3__16locale9use_facetERNS0_2idE Ltmp38: movq %rax, -344(%rbp) ## 8-byte Spill jmp LBB6_10 LBB6_10: ## %_ZNSt3__19use_facetINS_5ctypeIcEEEERKT_RKNS_6localeE.exit.i.i movb -41(%rbp), %al movq -344(%rbp), %rcx ## 8-byte Reload movq %rcx, -16(%rbp) movb %al, -17(%rbp) movq -16(%rbp), %rdx movq (%rdx), %rsi movq 56(%rsi), %rsi movsbl -17(%rbp), %edi Ltmp39: movl %edi, -348(%rbp) ## 4-byte Spill movq %rdx, %rdi movl -348(%rbp), %r8d ## 4-byte Reload movq %rsi, -360(%rbp) ## 8-byte Spill movl %r8d, %esi movq -360(%rbp), %rdx ## 8-byte Reload callq *%rdx Ltmp40: movb %al, -361(%rbp) ## 1-byte Spill jmp LBB6_14 LBB6_11: Ltmp41: movl %edx, %ecx movq %rax, -64(%rbp) movl %ecx, -68(%rbp) Ltmp42: leaq -56(%rbp), %rdi callq __ZNSt3__16localeD1Ev Ltmp43: jmp LBB6_12 LBB6_12: movq -64(%rbp), %rax movl -68(%rbp), %ecx movq %rax, -376(%rbp) ## 8-byte Spill movl %ecx, -380(%rbp) ## 4-byte Spill jmp LBB6_24 LBB6_13: Ltmp44: movl %edx, %ecx movq %rax, %rdi movl %ecx, -384(%rbp) ## 4-byte Spill callq ___clang_call_terminate LBB6_14: ## %_ZNKSt3__19basic_iosIcNS_11char_traitsIcEEE5widenEc.exit.i Ltmp45: leaq -56(%rbp), %rdi callq __ZNSt3__16localeD1Ev Ltmp46: jmp LBB6_15 LBB6_15: ## %.noexc1 movb -361(%rbp), %al ## 1-byte Reload movsbl %al, %ecx movq -336(%rbp), %rdx ## 8-byte Reload movl %ecx, 144(%rdx) LBB6_16: ## %_ZNKSt3__19basic_iosIcNS_11char_traitsIcEEE4fillEv.exit movq -336(%rbp), %rax ## 8-byte Reload movl 144(%rax), %ecx movb %cl, %dl movb %dl, -385(%rbp) ## 1-byte Spill ## BB#17: movq -264(%rbp), %rdi Ltmp47: movb -385(%rbp), %al ## 1-byte Reload movsbl %al, %r9d movq -288(%rbp), %rsi ## 8-byte Reload movq -312(%rbp), %rdx ## 8-byte Reload movq -320(%rbp), %rcx ## 8-byte Reload movq -328(%rbp), %r8 ## 8-byte Reload callq __ZNSt3__116__pad_and_outputIcNS_11char_traitsIcEEEENS_19ostreambuf_iteratorIT_T0_EES6_PKS4_S8_S8_RNS_8ios_baseES4_ Ltmp48: movq %rax, -400(%rbp) ## 8-byte Spill jmp LBB6_18 LBB6_18: leaq -272(%rbp), %rax movq -400(%rbp), %rcx ## 8-byte Reload movq %rcx, -272(%rbp) movq %rax, -88(%rbp) movq -88(%rbp), %rax cmpq $0, (%rax) jne LBB6_25 ## BB#19: movq -208(%rbp), %rax movq (%rax), %rcx movq -24(%rcx), %rcx addq %rcx, %rax movq %rax, -120(%rbp) movl $5, -124(%rbp) movq -120(%rbp), %rax movq %rax, -104(%rbp) movl $5, -108(%rbp) movq -104(%rbp), %rax movl 32(%rax), %edx orl $5, %edx Ltmp49: movq %rax, %rdi movl %edx, %esi callq __ZNSt3__18ios_base5clearEj Ltmp50: jmp LBB6_20 LBB6_20: ## %_ZNSt3__19basic_iosIcNS_11char_traitsIcEEE8setstateEj.exit jmp LBB6_21 LBB6_21: jmp LBB6_25 LBB6_22: Ltmp56: movl %edx, %ecx movq %rax, -248(%rbp) movl %ecx, -252(%rbp) jmp LBB6_29 LBB6_23: Ltmp51: movl %edx, %ecx movq %rax, -376(%rbp) ## 8-byte Spill movl %ecx, -380(%rbp) ## 4-byte Spill LBB6_24: ## %.body movl -380(%rbp), %eax ## 4-byte Reload movq -376(%rbp), %rcx ## 8-byte Reload movq %rcx, -248(%rbp) movl %eax, -252(%rbp) Ltmp52: leaq -240(%rbp), %rdi callq __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE6sentryD1Ev Ltmp53: jmp LBB6_28 LBB6_25: jmp LBB6_26 LBB6_26: Ltmp54: leaq -240(%rbp), %rdi callq __ZNSt3__113basic_ostreamIcNS_11char_traitsIcEEE6sentryD1Ev Ltmp55: jmp LBB6_27 LBB6_27: jmp LBB6_31 LBB6_28: jmp LBB6_29 LBB6_29: movq -248(%rbp), %rdi callq ___cxa_begin_catch movq -208(%rbp), %rdi movq (%rdi), %rcx movq -24(%rcx), %rcx addq %rcx, %rdi Ltmp57: movq %rax, -408(%rbp) ## 8-byte Spill callq __ZNSt3__18ios_base33__set_badbit_and_consider_rethrowEv Ltmp58: jmp LBB6_30 LBB6_30: callq ___cxa_end_catch LBB6_31: movq -208(%rbp), %rax addq $416, %rsp ## imm = 0x1A0 popq %rbp retq LBB6_32: Ltmp59: movl %edx, %ecx movq %rax, -248(%rbp) movl %ecx, -252(%rbp) Ltmp60: callq ___cxa_end_catch Ltmp61: jmp LBB6_33 LBB6_33: jmp LBB6_34 LBB6_34: movq -248(%rbp), %rdi callq __Unwind_Resume LBB6_35: Ltmp62: movl %edx, %ecx movq %rax, %rdi movl %ecx, -412(%rbp) ## 4-byte Spill callq ___clang_call_terminate .cfi_endproc Leh_func_end6: .section __TEXT,__gcc_except_tab .align 2 GCC_except_table6: Lexception6: .byte 255 ## @LPStart Encoding = omit .byte 155 ## @TType Encoding = indirect pcrel sdata4 .asciz "253201" ## @TType base offset .byte 3 ## Call site Encoding = udata4 .ascii "234 01" ## Call site table length Lset10 = Ltmp33-Leh_func_begin6 ## >> Call Site 1 << .long Lset10 Lset11 = Ltmp34-Ltmp33 ## Call between Ltmp33 and Ltmp34 .long Lset11 Lset12 = Ltmp56-Leh_func_begin6 ## jumps to Ltmp56 .long Lset12 .byte 5 ## On action: 3 Lset13 = Ltmp35-Leh_func_begin6 ## >> Call Site 2 << .long Lset13 Lset14 = Ltmp36-Ltmp35 ## Call between Ltmp35 and Ltmp36 .long Lset14 Lset15 = Ltmp51-Leh_func_begin6 ## jumps to Ltmp51 .long Lset15 .byte 5 ## On action: 3 Lset16 = Ltmp37-Leh_func_begin6 ## >> Call Site 3 << .long Lset16 Lset17 = Ltmp40-Ltmp37 ## Call between Ltmp37 and Ltmp40 .long Lset17 Lset18 = Ltmp41-Leh_func_begin6 ## jumps to Ltmp41 .long Lset18 .byte 3 ## On action: 2 Lset19 = Ltmp42-Leh_func_begin6 ## >> Call Site 4 << .long Lset19 Lset20 = Ltmp43-Ltmp42 ## Call between Ltmp42 and Ltmp43 .long Lset20 Lset21 = Ltmp44-Leh_func_begin6 ## jumps to Ltmp44 .long Lset21 .byte 7 ## On action: 4 Lset22 = Ltmp45-Leh_func_begin6 ## >> Call Site 5 << .long Lset22 Lset23 = Ltmp50-Ltmp45 ## Call between Ltmp45 and Ltmp50 .long Lset23 Lset24 = Ltmp51-Leh_func_begin6 ## jumps to Ltmp51 .long Lset24 .byte 5 ## On action: 3 Lset25 = Ltmp52-Leh_func_begin6 ## >> Call Site 6 << .long Lset25 Lset26 = Ltmp53-Ltmp52 ## Call between Ltmp52 and Ltmp53 .long Lset26 Lset27 = Ltmp62-Leh_func_begin6 ## jumps to Ltmp62 .long Lset27 .byte 5 ## On action: 3 Lset28 = Ltmp54-Leh_func_begin6 ## >> Call Site 7 << .long Lset28 Lset29 = Ltmp55-Ltmp54 ## Call between Ltmp54 and Ltmp55 .long Lset29 Lset30 = Ltmp56-Leh_func_begin6 ## jumps to Ltmp56 .long Lset30 .byte 5 ## On action: 3 Lset31 = Ltmp55-Leh_func_begin6 ## >> Call Site 8 << .long Lset31 Lset32 = Ltmp57-Ltmp55 ## Call between Ltmp55 and Ltmp57 .long Lset32 .long 0 ## has no landing pad .byte 0 ## On action: cleanup Lset33 = Ltmp57-Leh_func_begin6 ## >> Call Site 9 << .long Lset33 Lset34 = Ltmp58-Ltmp57 ## Call between Ltmp57 and Ltmp58 .long Lset34 Lset35 = Ltmp59-Leh_func_begin6 ## jumps to Ltmp59 .long Lset35 .byte 0 ## On action: cleanup Lset36 = Ltmp58-Leh_func_begin6 ## >> Call Site 10 << .long Lset36 Lset37 = Ltmp60-Ltmp58 ## Call between Ltmp58 and Ltmp60 .long Lset37 .long 0 ## has no landing pad .byte 0 ## On action: cleanup Lset38 = Ltmp60-Leh_func_begin6 ## >> Call Site 11 << .long Lset38 Lset39 = Ltmp61-Ltmp60 ## Call between Ltmp60 and Ltmp61 .long Lset39 Lset40 = Ltmp62-Leh_func_begin6 ## jumps to Ltmp62 .long Lset40 .byte 5 ## On action: 3 Lset41 = Ltmp61-Leh_func_begin6 ## >> Call Site 12 << .long Lset41 Lset42 = Leh_func_end6-Ltmp61 ## Call between Ltmp61 and Leh_func_end6 .long Lset42 .long 0 ## has no landing pad .byte 0 ## On action: cleanup .byte 0 ## >> Action Record 1 << ## Cleanup .byte 0 ## No further actions .byte 1 ## >> Action Record 2 << ## Catch TypeInfo 1 .byte 125 ## Continue to action 1 .byte 1 ## >> Action Record 3 << ## Catch TypeInfo 1 .byte 0 ## No further actions .byte 1 ## >> Action Record 4 << ## Catch TypeInfo 1 .byte 125 ## Continue to action 3 ## >> Catch TypeInfos << .long 0 ## TypeInfo 1 .align 2 .section __TEXT,__textcoal_nt,coalesced,pure_instructions .private_extern __ZNSt3__116__pad_and_outputIcNS_11char_traitsIcEEEENS_19ostreambuf_iteratorIT_T0_EES6_PKS4_S8_S8_RNS_8ios_baseES4_ .globl __ZNSt3__116__pad_and_outputIcNS_11char_traitsIcEEEENS_19ostreambuf_iteratorIT_T0_EES6_PKS4_S8_S8_RNS_8ios_baseES4_ .weak_def_can_be_hidden __ZNSt3__116__pad_and_outputIcNS_11char_traitsIcEEEENS_19ostreambuf_iteratorIT_T0_EES6_PKS4_S8_S8_RNS_8ios_baseES4_ .align 4, 0x90 __ZNSt3__116__pad_and_outputIcNS_11char_traitsIcEEEENS_19ostreambuf_iteratorIT_T0_EES6_PKS4_S8_S8_RNS_8ios_baseES4_: ## @_ZNSt3__116__pad_and_outputIcNS_11char_traitsIcEEEENS_19ostreambuf_iteratorIT_T0_EES6_PKS4_S8_S8_RNS_8ios_baseES4_ .cfi_startproc .cfi_personality 155, ___gxx_personality_v0 Leh_func_begin7: .cfi_lsda 16, Lexception7 ## BB#0: pushq %rbp Ltmp76: .cfi_def_cfa_offset 16 Ltmp77: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp78: .cfi_def_cfa_register %rbp subq $720, %rsp ## imm = 0x2D0 movb %r9b, %al leaq -552(%rbp), %r10 leaq -488(%rbp), %r11 movq %rdi, -504(%rbp) movq %rsi, -512(%rbp) movq %rdx, -520(%rbp) movq %rcx, -528(%rbp) movq %r8, -536(%rbp) movb %al, -537(%rbp) movq -504(%rbp), %rcx movq %r11, -472(%rbp) movq $-1, -480(%rbp) movq -472(%rbp), %rdx movq -480(%rbp), %rsi movq %rdx, -456(%rbp) movq %rsi, -464(%rbp) movq -456(%rbp), %rdx movq $0, (%rdx) movq -488(%rbp), %rdx movq %rdx, -552(%rbp) movq %r10, -448(%rbp) cmpq $0, %rcx jne LBB7_2 ## BB#1: movq -504(%rbp), %rax movq %rax, -496(%rbp) jmp LBB7_29 LBB7_2: movq -528(%rbp), %rax movq -512(%rbp), %rcx subq %rcx, %rax movq %rax, -560(%rbp) movq -536(%rbp), %rax movq %rax, -344(%rbp) movq -344(%rbp), %rax movq 24(%rax), %rax movq %rax, -568(%rbp) movq -568(%rbp), %rax cmpq -560(%rbp), %rax jle LBB7_4 ## BB#3: movq -560(%rbp), %rax movq -568(%rbp), %rcx subq %rax, %rcx movq %rcx, -568(%rbp) jmp LBB7_5 LBB7_4: movq $0, -568(%rbp) LBB7_5: movq -520(%rbp), %rax movq -512(%rbp), %rcx subq %rcx, %rax movq %rax, -576(%rbp) cmpq $0, -576(%rbp) jle LBB7_9 ## BB#6: movq -504(%rbp), %rax movq -512(%rbp), %rcx movq -576(%rbp), %rdx movq %rax, -248(%rbp) movq %rcx, -256(%rbp) movq %rdx, -264(%rbp) movq -248(%rbp), %rax movq (%rax), %rcx movq 96(%rcx), %rcx movq -256(%rbp), %rsi movq -264(%rbp), %rdx movq %rax, %rdi callq *%rcx cmpq -576(%rbp), %rax je LBB7_8 ## BB#7: leaq -584(%rbp), %rax leaq -240(%rbp), %rcx movq %rcx, -224(%rbp) movq $-1, -232(%rbp) movq -224(%rbp), %rcx movq -232(%rbp), %rdx movq %rcx, -208(%rbp) movq %rdx, -216(%rbp) movq -208(%rbp), %rcx movq $0, (%rcx) movq -240(%rbp), %rcx movq %rcx, -584(%rbp) movq %rax, -8(%rbp) movq $0, -504(%rbp) movq -504(%rbp), %rax movq %rax, -496(%rbp) jmp LBB7_29 LBB7_8: jmp LBB7_9 LBB7_9: cmpq $0, -568(%rbp) jle LBB7_24 ## BB#10: leaq -608(%rbp), %rax movq -568(%rbp), %rcx movb -537(%rbp), %dl movq %rax, -72(%rbp) movq %rcx, -80(%rbp) movb %dl, -81(%rbp) movq -72(%rbp), %rax movq -80(%rbp), %rcx movb -81(%rbp), %dl movq %rax, -48(%rbp) movq %rcx, -56(%rbp) movb %dl, -57(%rbp) movq -48(%rbp), %rax movq %rax, -40(%rbp) movq -40(%rbp), %rcx movq %rcx, -32(%rbp) movq -32(%rbp), %rcx movq %rcx, -24(%rbp) movq -24(%rbp), %rcx movq %rcx, -16(%rbp) movq -56(%rbp), %rsi movq %rax, %rdi movsbl -57(%rbp), %edx callq __ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEmc leaq -608(%rbp), %rax movq -504(%rbp), %rcx movq %rax, -200(%rbp) movq -200(%rbp), %rax movq %rax, -192(%rbp) movq -192(%rbp), %rax movq %rax, -184(%rbp) movq -184(%rbp), %rsi movq %rsi, -176(%rbp) movq -176(%rbp), %rsi movq %rsi, -168(%rbp) movq -168(%rbp), %rsi movzbl (%rsi), %edx andl $1, %edx cmpl $0, %edx movq %rcx, -656(%rbp) ## 8-byte Spill movq %rax, -664(%rbp) ## 8-byte Spill je LBB7_12 ## BB#11: movq -664(%rbp), %rax ## 8-byte Reload movq %rax, -120(%rbp) movq -120(%rbp), %rcx movq %rcx, -112(%rbp) movq -112(%rbp), %rcx movq %rcx, -104(%rbp) movq -104(%rbp), %rcx movq 16(%rcx), %rcx movq %rcx, -672(%rbp) ## 8-byte Spill jmp LBB7_13 LBB7_12: movq -664(%rbp), %rax ## 8-byte Reload movq %rax, -160(%rbp) movq -160(%rbp), %rcx movq %rcx, -152(%rbp) movq -152(%rbp), %rcx movq %rcx, -144(%rbp) movq -144(%rbp), %rcx addq $1, %rcx movq %rcx, -136(%rbp) movq -136(%rbp), %rcx movq %rcx, -128(%rbp) movq -128(%rbp), %rcx movq %rcx, -672(%rbp) ## 8-byte Spill LBB7_13: ## %_ZNKSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE4dataEv.exit movq -672(%rbp), %rax ## 8-byte Reload movq %rax, -96(%rbp) movq -568(%rbp), %rcx movq -656(%rbp), %rdx ## 8-byte Reload movq %rdx, -272(%rbp) movq %rax, -280(%rbp) movq %rcx, -288(%rbp) movq -272(%rbp), %rax movq (%rax), %rsi movq 96(%rsi), %rsi movq -280(%rbp), %rdi Ltmp68: movq %rdi, -680(%rbp) ## 8-byte Spill movq %rax, %rdi movq -680(%rbp), %rax ## 8-byte Reload movq %rsi, -688(%rbp) ## 8-byte Spill movq %rax, %rsi movq %rcx, %rdx movq -688(%rbp), %rcx ## 8-byte Reload callq *%rcx Ltmp69: movq %rax, -696(%rbp) ## 8-byte Spill jmp LBB7_14 LBB7_14: ## %_ZNSt3__115basic_streambufIcNS_11char_traitsIcEEE5sputnEPKcl.exit jmp LBB7_15 LBB7_15: movq -696(%rbp), %rax ## 8-byte Reload cmpq -568(%rbp), %rax je LBB7_20 ## BB#16: leaq -328(%rbp), %rax movq %rax, -312(%rbp) movq $-1, -320(%rbp) movq -312(%rbp), %rax movq -320(%rbp), %rcx movq %rax, -296(%rbp) movq %rcx, -304(%rbp) movq -296(%rbp), %rax movq $0, (%rax) movq -328(%rbp), %rax movq %rax, -704(%rbp) ## 8-byte Spill ## BB#17: leaq -632(%rbp), %rax movq -704(%rbp), %rcx ## 8-byte Reload movq %rcx, -632(%rbp) movq %rax, -336(%rbp) ## BB#18: movq $0, -504(%rbp) movq -504(%rbp), %rax movq %rax, -496(%rbp) movl $1, -636(%rbp) jmp LBB7_21 LBB7_19: Ltmp70: movl %edx, %ecx movq %rax, -616(%rbp) movl %ecx, -620(%rbp) Ltmp71: leaq -608(%rbp), %rdi callq __ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEED1Ev Ltmp72: jmp LBB7_23 LBB7_20: movl $0, -636(%rbp) LBB7_21: leaq -608(%rbp), %rdi callq __ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEED1Ev movl -636(%rbp), %eax movl %eax, %ecx subl $1, %ecx movl %eax, -708(%rbp) ## 4-byte Spill movl %ecx, -712(%rbp) ## 4-byte Spill je LBB7_29 jmp LBB7_33 LBB7_33: movl -708(%rbp), %eax ## 4-byte Reload testl %eax, %eax jne LBB7_32 jmp LBB7_22 LBB7_22: jmp LBB7_24 LBB7_23: jmp LBB7_30 LBB7_24: movq -528(%rbp), %rax movq -520(%rbp), %rcx subq %rcx, %rax movq %rax, -576(%rbp) cmpq $0, -576(%rbp) jle LBB7_28 ## BB#25: movq -504(%rbp), %rax movq -520(%rbp), %rcx movq -576(%rbp), %rdx movq %rax, -352(%rbp) movq %rcx, -360(%rbp) movq %rdx, -368(%rbp) movq -352(%rbp), %rax movq (%rax), %rcx movq 96(%rcx), %rcx movq -360(%rbp), %rsi movq -368(%rbp), %rdx movq %rax, %rdi callq *%rcx cmpq -576(%rbp), %rax je LBB7_27 ## BB#26: leaq -648(%rbp), %rax leaq -408(%rbp), %rcx movq %rcx, -392(%rbp) movq $-1, -400(%rbp) movq -392(%rbp), %rcx movq -400(%rbp), %rdx movq %rcx, -376(%rbp) movq %rdx, -384(%rbp) movq -376(%rbp), %rcx movq $0, (%rcx) movq -408(%rbp), %rcx movq %rcx, -648(%rbp) movq %rax, -416(%rbp) movq $0, -504(%rbp) movq -504(%rbp), %rax movq %rax, -496(%rbp) jmp LBB7_29 LBB7_27: jmp LBB7_28 LBB7_28: movq -536(%rbp), %rax movq %rax, -424(%rbp) movq $0, -432(%rbp) movq -424(%rbp), %rax movq 24(%rax), %rcx movq %rcx, -440(%rbp) movq -432(%rbp), %rcx movq %rcx, 24(%rax) movq -504(%rbp), %rax movq %rax, -496(%rbp) LBB7_29: movq -496(%rbp), %rax addq $720, %rsp ## imm = 0x2D0 popq %rbp retq LBB7_30: movq -616(%rbp), %rdi callq __Unwind_Resume LBB7_31: Ltmp73: movl %edx, %ecx movq %rax, %rdi movl %ecx, -716(%rbp) ## 4-byte Spill callq ___clang_call_terminate LBB7_32: .cfi_endproc Leh_func_end7: .section __TEXT,__gcc_except_tab .align 2 GCC_except_table7: Lexception7: .byte 255 ## @LPStart Encoding = omit .byte 155 ## @TType Encoding = indirect pcrel sdata4 .asciz "274" ## @TType base offset .byte 3 ## Call site Encoding = udata4 .byte 52 ## Call site table length Lset43 = Leh_func_begin7-Leh_func_begin7 ## >> Call Site 1 << .long Lset43 Lset44 = Ltmp68-Leh_func_begin7 ## Call between Leh_func_begin7 and Ltmp68 .long Lset44 .long 0 ## has no landing pad .byte 0 ## On action: cleanup Lset45 = Ltmp68-Leh_func_begin7 ## >> Call Site 2 << .long Lset45 Lset46 = Ltmp69-Ltmp68 ## Call between Ltmp68 and Ltmp69 .long Lset46 Lset47 = Ltmp70-Leh_func_begin7 ## jumps to Ltmp70 .long Lset47 .byte 0 ## On action: cleanup Lset48 = Ltmp71-Leh_func_begin7 ## >> Call Site 3 << .long Lset48 Lset49 = Ltmp72-Ltmp71 ## Call between Ltmp71 and Ltmp72 .long Lset49 Lset50 = Ltmp73-Leh_func_begin7 ## jumps to Ltmp73 .long Lset50 .byte 1 ## On action: 1 Lset51 = Ltmp72-Leh_func_begin7 ## >> Call Site 4 << .long Lset51 Lset52 = Leh_func_end7-Ltmp72 ## Call between Ltmp72 and Leh_func_end7 .long Lset52 .long 0 ## has no landing pad .byte 0 ## On action: cleanup .byte 1 ## >> Action Record 1 << ## Catch TypeInfo 1 .byte 0 ## No further actions ## >> Catch TypeInfos << .long 0 ## TypeInfo 1 .align 2 .section __TEXT,__textcoal_nt,coalesced,pure_instructions .globl __ZN6MatrixC2Ed .weak_def_can_be_hidden __ZN6MatrixC2Ed .align 4, 0x90 __ZN6MatrixC2Ed: ## @_ZN6MatrixC2Ed .cfi_startproc ## BB#0: pushq %rbp Ltmp81: .cfi_def_cfa_offset 16 Ltmp82: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp83: .cfi_def_cfa_register %rbp subq $64, %rsp movq __ZNSt3__14coutE@GOTPCREL(%rip), %rax leaq L_.str2(%rip), %rsi movq %rdi, -24(%rbp) movsd %xmm0, -32(%rbp) movq -24(%rbp), %rdi movq %rdi, -48(%rbp) ## 8-byte Spill movq %rax, %rdi callq __ZNSt3__1lsINS_11char_traitsIcEEEERNS_13basic_ostreamIcT_EES6_PKc leaq __ZNSt3__14endlIcNS_11char_traitsIcEEEERNS_13basic_ostreamIT_T0_EES7_(%rip), %rsi movq %rax, -8(%rbp) movq %rsi, -16(%rbp) movq -8(%rbp), %rdi callq *-16(%rbp) movl $0, -36(%rbp) movq %rax, -56(%rbp) ## 8-byte Spill LBB8_1: ## =>This Loop Header: Depth=1 ## Child Loop BB8_3 Depth 2 cmpl $10, -36(%rbp) jge LBB8_8 ## BB#2: ## in Loop: Header=BB8_1 Depth=1 movl $0, -40(%rbp) LBB8_3: ## Parent Loop BB8_1 Depth=1 ## => This Inner Loop Header: Depth=2 cmpl $10, -40(%rbp) jge LBB8_6 ## BB#4: ## in Loop: Header=BB8_3 Depth=2 movsd -32(%rbp), %xmm0 movslq -40(%rbp), %rax movslq -36(%rbp), %rcx imulq $80, %rcx, %rcx movq -48(%rbp), %rdx ## 8-byte Reload addq %rcx, %rdx movsd %xmm0, (%rdx,%rax,8) ## BB#5: ## in Loop: Header=BB8_3 Depth=2 movl -40(%rbp), %eax addl $1, %eax movl %eax, -40(%rbp) jmp LBB8_3 LBB8_6: ## in Loop: Header=BB8_1 Depth=1 jmp LBB8_7 LBB8_7: ## in Loop: Header=BB8_1 Depth=1 movl -36(%rbp), %eax addl $1, %eax movl %eax, -36(%rbp) jmp LBB8_1 LBB8_8: addq $64, %rsp popq %rbp retq .cfi_endproc .section __TEXT,__cstring,cstring_literals L_.str: ## @.str .asciz "Address of sum: " L_.str1: ## @.str1 .asciz "Address of c: " L_.str2: ## @.str2 .asciz "Matrix::Matrix()" .section __TEXT,__eh_frame,coalesced,no_toc+strip_static_syms+live_support .subsections_via_symbols
而这时简化版的代码（突出返回临时对象）：
#include <iostream> #include <cstring> using namespace std; class Matrix { public: explicit Matrix() { } friend const Matrix operator+(const Matrix&, const Matrix&); }; const Matrix operator+(const Matrix& arg1, const Matrix& arg2) { Matrix sum; return sum; } int main() { Matrix a, b; Matrix c = (a + b); return 0; }
汇编：
.section __TEXT,__text,regular,pure_instructions .globl __ZplRK6MatrixS1_ .align 4, 0x90 __ZplRK6MatrixS1_: ## @_ZplRK6MatrixS1_ .cfi_startproc ## BB#0: pushq %rbp Ltmp2: .cfi_def_cfa_offset 16 Ltmp3: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp4: .cfi_def_cfa_register %rbp subq $32, %rsp leaq -8(%rbp), %rax movq %rdi, -16(%rbp) movq %rsi, -24(%rbp) movq %rax, %rdi callq __ZN6MatrixC1Ev addq $32, %rsp popq %rbp retq .cfi_endproc .section __TEXT,__textcoal_nt,coalesced,pure_instructions .globl __ZN6MatrixC1Ev .weak_def_can_be_hidden __ZN6MatrixC1Ev .align 4, 0x90 __ZN6MatrixC1Ev: ## @_ZN6MatrixC1Ev .cfi_startproc ## BB#0: pushq %rbp Ltmp7: .cfi_def_cfa_offset 16 Ltmp8: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp9: .cfi_def_cfa_register %rbp subq $16, %rsp movq %rdi, -8(%rbp) movq -8(%rbp), %rdi callq __ZN6MatrixC2Ev addq $16, %rsp popq %rbp retq .cfi_endproc .section __TEXT,__text,regular,pure_instructions .globl _main .align 4, 0x90 _main: ## @main .cfi_startproc ## BB#0: pushq %rbp Ltmp12: .cfi_def_cfa_offset 16 Ltmp13: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp14: .cfi_def_cfa_register %rbp subq $32, %rsp leaq -8(%rbp), %rdi movl $0, -4(%rbp) callq __ZN6MatrixC1Ev leaq -16(%rbp), %rdi callq __ZN6MatrixC1Ev leaq -8(%rbp), %rdi leaq -16(%rbp), %rsi callq __ZplRK6MatrixS1_ movl $0, %eax addq $32, %rsp popq %rbp retq .cfi_endproc .section __TEXT,__textcoal_nt,coalesced,pure_instructions .globl __ZN6MatrixC2Ev .weak_def_can_be_hidden __ZN6MatrixC2Ev .align 4, 0x90 __ZN6MatrixC2Ev: ## @_ZN6MatrixC2Ev .cfi_startproc ## BB#0: pushq %rbp Ltmp17: .cfi_def_cfa_offset 16 Ltmp18: .cfi_offset %rbp, -16 movq %rsp, %rbp Ltmp19: .cfi_def_cfa_register %rbp movq %rdi, -8(%rbp) popq %rbp retq .cfi_endproc .subsections_via_symbols