目录
编译过程查看
main.m文件内容如下
#import <Foundation/Foundation.h>
#import "Person.h"
#define AGE (18)
int main(int argc, const char * argv[]) {
@autoreleasepool {
int a = 10;
int b = 20;
int c = a+b+AGE;
printf("c = %d\n",c);
}
return 0;
}
查看main.m文件的执行过程
clang -ccc-print-phases main.m
执行过程如下
$ clang -ccc-print-phases -framework Foundation main.m -o main
0: input, "Foundation", object //导入Foundation框架
1: input, "main.m", objective-c //导入源文件
2: preprocessor, {1}, objective-c-cpp-output //预处理
3: compiler, {2}, ir //编译生成IR(中间代码)
4: backend, {3}, assembler //汇编器生成汇编代码
5: assembler, {4}, object //生成机器码
6: linker, {0, 5}, image //链接
7: bind-arch, "x86_64", {6}, image //生成Image，也就是最后的可执行文件
接着，就可以在终端直接运行这个程序了：
$ ./main
编译过程
一、预处理
指令
clang -E main.m -o emain.m
emain.m文件如下
@interface Person : NSObject
@end
int main(int argc, const char * argv[]) {
@autoreleasepool {
int a = 10;
int b = 20;
int c = a+b+(18);
print("c = %d\n",c);
}
return 0;
}
替换了Person.h文件的内容和宏定义
二、词法分析，生成Token
clang -fmodules -E -Xclang -dump-tokens main.m
部分代码
at '@' [StartOfLine] Loc=<./Person.h:15:1>
identifier 'interface' Loc=<./Person.h:15:2>
identifier 'Person' [LeadingSpace] Loc=<./Person.h:15:12>
colon ':' [LeadingSpace] Loc=<./Person.h:15:19>
identifier 'NSObject' [LeadingSpace] Loc=<./Person.h:15:21>
at '@' [StartOfLine] Loc=<./Person.h:19:1>
identifier 'end' Loc=<./Person.h:19:2>
int 'int' [StartOfLine] Loc=<main.m:14:1>
identifier 'main' [LeadingSpace] Loc=<main.m:14:5>
l_paren '(' Loc=<main.m:14:9>
int 'int' Loc=<main.m:14:10>
identifier 'argc' [LeadingSpace] Loc=<main.m:14:14>
comma ',' Loc=<main.m:14:18>
三、语法分析，生成语法树(AST,AbstractSyntax Tree)
$clang -fmodules -fsyntax-only -Xclang -ast-dump main.m
部分代码
-FunctionDecl 0x7f7fde294740 <main.m:14:1, line:22:1> line:14:5 main 'int (int, const char **)'
| |-ParmVarDecl 0x7f7fde2944e8 <col:10, col:14> col:14 argc 'int'
| |-ParmVarDecl 0x7f7fde294600 <col:20, col:38> col:33 argv 'const char **':'const char **'
| `-CompoundStmt 0x7f7fdf01e488 <col:41, line:22:1>
| |-ObjCAutoreleasePoolStmt 0x7f7fdf01e440 <line:15:5, line:20:5>
| | `-CompoundStmt 0x7f7fdf01e410 <line:15:22, line:20:5>
| | |-DeclStmt 0x7f7fde294908 <line:16:9, col:19>
| | | `-VarDecl 0x7f7fde294888 <col:9, col:17> col:13 used a 'int' cinit
| | | `-IntegerLiteral 0x7f7fde2948e8 <col:17> 'int' 10
| | |-DeclStmt 0x7f7fde2949b8 <line:17:9, col:19>
| | | `-VarDecl 0x7f7fde294938 <col:9, col:17> col:13 used b 'int' cinit
| | | `-IntegerLiteral 0x7f7fde294998 <col:17> 'int' 20
四、生成中间代码IR
LLVM IR有3种表示形式(但本质是等价的，就好比水可以有气体，液体，固体等3中形态）
text:便于阅读的文本格式，类似于汇编语言，扩展名.ll
clang -S -emit-llvm main.m -o main.ll
main.ll文件的部分内容
Function Attrs: noinline optnone ssp uwtable
define i32 @main(i32, i8**) #0 {
%3 = alloca i32, align 4
%4 = alloca i32, align 4
%5 = alloca i8**, align 8
%6 = alloca i32, align 4
%7 = alloca i32, align 4
%8 = alloca i32, align 4
store i32 0, i32* %3, align 4
store i32 %0, i32* %4, align 4
store i8** %1, i8*** %5, align 8
%9 = call i8* @llvm.objc.autoreleasePoolPush() #1
store i32 10, i32* %6, align 4
store i32 20, i32* %7, align 4
%10 = load i32, i32* %6, align 4
%11 = load i32, i32* %7, align 4
%12 = add nsw i32 %10, %11
%13 = add nsw i32 %12, 18
store i32 %13, i32* %8, align 4
%14 = load i32, i32* %8, align 4
%15 = call i32 (i8*, i32, ...) bitcast (i32 (...)* @print to i32 (i8*, i32, ...)*)(i8* getelementptr inbounds ([8 x i8], [8 x i8]* @.str, i32 0, i32 0), i32 %14)
call void @llvm.objc.autoreleasePoolPop(i8* %9)
ret i32 0
}
bitcode：二进制格式，扩展名为.bc
clang -c -emit-llvm main.m
查看main.bc文件
hexdump -C main.bc | head
00000000 de c0 17 0b 00 00 00 00 14 00 00 00 90 0d 00 00 |................|
00000010 07 00 00 01 42 43 c0 de 35 14 00 00 07 00 00 00 |....BC..5.......|
00000020 62 0c 30 24 96 96 a6 a5 f7 d7 7f 5d d3 b4 4f fb |b.0$.......]..O.|
00000030 f7 ed d7 fb 4f 0b 51 80 4c 01 00 00 21 0c 00 00 |....O.Q.L...!...|
00000040 ee 02 00 00 0b 02 21 00 02 00 00 00 16 00 00 00 |......!.........|
00000050 07 81 23 91 41 c8 04 49 06 10 32 39 92 01 84 0c |..#.A..I..29....|
00000060 25 05 08 19 1e 04 8b 62 80 14 45 02 42 92 0b 42 |%......b..E.B..B|
00000070 a4 10 32 14 38 08 18 4b 0a 32 52 88 48 70 c4 21 |..2.8..K.2R.Hp.!|
00000080 23 44 12 87 8c 10 41 92 02 64 c8 08 b1 14 20 43 |#D....A..d.... C|
00000090 46 88 20 c9 01 32 52 84 18 2a 28 2a 90 31 7c b0 |F. ..2R..*(*.1|.|
memory:内存格式
五、生成汇编
clang -S -fobjc-arc main.m -o main.s
main.s部分内容
_main: ## @main
.cfi_startproc
## %bb.0:
pushq %rbp
.cfi_def_cfa_offset 16
.cfi_offset %rbp, -16
movq %rsp, %rbp
.cfi_def_cfa_register %rbp
subq $48, %rsp
movl $0, -4(%rbp)
movl %edi, -8(%rbp)
movq %rsi, -16(%rbp)
callq _objc_autoreleasePoolPush
movl $10, -20(%rbp)
movl $20, -24(%rbp)
movl -20(%rbp), %edi
addl -24(%rbp), %edi
六、生成目标文件
clang -fmodules -c main.m -o main.o
七、生成可执行文件，这样就能够执行看到输出结果
clang main.o -o main
或者
clang main.m -o main -framework Foundation
八、执行
./main
执行结果
c = 48
行者常至，为者常成！