C - Cpp

Yayu Wang included in category Programming_languages

2022-04-20 2024-04-24 3080 words 14 minutes

Dynamic library

compile

The -fPIC flag stands for 'Position Independent Code' generation

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gcc -shared -fPIC -o libFct.so fct.o

Makefile

@

$@ represents the target of the current rule

^

$^ represents all the prerequisites (dependencies) of the current rule

assembly

sample

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int src = 1;
int dst;

asm("mov %1, %0;"
    "add $1, %0;"
    : "=r"(dst)
    : "r"(src));

printf("%d\n", dst);

syntax

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asm asm-qualifiers ( AssemblerTemplate
                 : OutputOperands
                 [ : InputOperands
                 [ : Clobbers ] ])

Qualifiers

volatile
inline
goto

Parameters

AssemblerTemplate

This is a literal string that is the template for the assembler code. It is a combination of fixed text and tokens that refer to the input, output, and goto parameters.

Special format strings

Outputs a single % into the assembler code.

Outputs a number that is unique to each instance of the asm statement in the entire compilation. This option is useful when creating local labels and referring to them multiple times in a single template that generates multiple assembler instructions.

%{ %| %}

Outputs {, |, and } characters (respectively) into the assembler code. When unescaped, these characters have special meaning to indicate multiple assembler dialects, as described below.

dialect

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"bt{l %[Offset],%[Base] | %[Base],%[Offset]}; jc %l2"

// is equivalent to one of

"btl %[Offset],%[Base] ; jc %l2"   /* att dialect */
"bt %[Base],%[Offset]; jc %l2"     /* intel dialect */

OutputOperands

A comma-separated list of the C variables modified by the instructions in the AssemblerTemplate. An empty list is permitted.
[ [asmSymbolicName] ] constraint (cvariablename)

asmSymbolicName

%[ref_name]

constraint

Output constraints must begin with either = (a variable overwriting an existing value) or + (when reading and writing).
Common constraints include r for register and m for memory. When you list more than one possible location (for example, "=rm"), the compiler chooses the most efficient one based on the current context.

cvariablename

Specifies a C lvalue expression to hold the output, typically a variable name.

InputOperands

A comma-separated list of C expressions read by the instructions in the AssemblerTemplate. An empty list is permitted.

Clobbers

A comma-separated list of registers or other values changed by the AssemblerTemplate, beyond those listed as outputs. An empty list is permitted.

GotoLabels

When you are using the goto form of asm, this section contains the list of all C labels to which the code in the AssemblerTemplate may jump.

Constraints

Simple Constraints

compile

object file

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gcc -g -O -c main.c

keywords

static

static function

A static function is visible only in the file it's declared in

static variable

A static global variable is visible only in the file it's declared in
A static local variable is a Singleton in the block it's declared in

volatile

volatile variable

Volatile keyword indicates that a value may change between different accesses, so compiler shall not to optimize anything related to the volatile varible

mutex/semaphore

across processes

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sem_t* sem;
sem = sem_open("/semaphore", O_CREAT, 0644, 1);
sem_init(sem, 1, 0);

sem_post(sem); // +1
sem_wait(sem); // wait -1

typedef

syntax

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typedef <existing_data_type> <new_data_type_name>;

sample

array

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typedef int sixteen_int_array[16];
// type \Rightarrow int(*)[16];
sixteen_int_array arr;
// equal uint32_t (*arr)[16];
arr = calloc(16, sizeof(uint32_t));

struct

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typedef struct sample_struct {
  int a;
  char b;
} struct_t;

function pointer

return type: int, arguments: (int, char)

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typedef int (*func_ptr_t)(int, char);

memory

calloc

alocated with 0

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void* calloc(size_t num, size_t size);
int* arr;
arr = (int*)calloc(16, sizeof(int)); // a[16] = {0}

file

FILE write

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char* filename = "file.txt";
FILE* fp;
// Open the file for writing in binary mode
fp = fopen(filename, "wb");
if (fp == NULL) {
    fprintf(stderr, "Error opening file %s\n", filename);
    exit(1);
 }
char buffer[128] = {};
sprintf(buffer, "write to file: %s", filename);
fwrite(buffer, sizeof(char), strlen(buffer), fp);
fclose(fp);

errors

error: variably modified ‘diff’ at file scope

use define in c instead of const

string

substring

find first matching suffix

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  #include <string.h>

  char str[] = "This is a simple string";
  char *pch;
  pch = strstr(str, "simple"); // = "sample example"

convert

to integer

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const char* istr = "123567";
int i = atoi(istr);

to double

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const char* dstr = "1.42857";
double d = atof(dst);

copy

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#include<string.h>

const char *password = "5pX!07&YpKNfnAFzSTWyyyyyyy";
strncpy(passwd, password, 16); // = "5pX!07&YpKNfnAFz"

cmake

add compilation options

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add_compile_options(-g)

cmdline

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cmake .. -DCMAKE_BUILD_TYPE=Debug

cmake message

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message("echo ${VARIABLE} in shell")

clang-format

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# 语言: None, Cpp, Java, JavaScript, ObjC, Proto, TableGen, TextProto
Language: Cpp

# BasedOnStyle
BasedOnStyle: LLVM

# 访问说明符(public、private等)的偏移
AccessModifierOffset: -4

# 开括号(开圆括号、开尖括号、开方括号)后的对齐: Align, DontAlign, AlwaysBreak(总是在开括号后换行)
AlignAfterOpenBracket: Align

# 连续赋值时，对齐所有等号
AlignConsecutiveAssignments: true

# 连续声明时，对齐所有声明的变量名
AlignConsecutiveDeclarations: true

# 左对齐逃脱换行(使用反斜杠换行)的反斜杠
AlignEscapedNewlinesLeft: true

# 水平对齐二元和三元表达式的操作数
AlignOperands: true

# 对齐连续的尾随的注释
AlignTrailingComments: true

# 允许函数声明的所有参数在放在下一行
AllowAllParametersOfDeclarationOnNextLine: true

# 允许短的块放在同一行
AllowShortBlocksOnASingleLine: false

# 允许短的case标签放在同一行
AllowShortCaseLabelsOnASingleLine: false

# 允许短的函数放在同一行: None, InlineOnly(定义在类中), Empty(空函数), Inline(定义在类中，空函数), All
AllowShortFunctionsOnASingleLine: Empty

# 允许短的if语句保持在同一行
AllowShortIfStatementsOnASingleLine: false

# 允许短的循环保持在同一行
AllowShortLoopsOnASingleLine: false

# 总是在定义返回类型后换行(deprecated)
AlwaysBreakAfterDefinitionReturnType: None

# 总是在返回类型后换行: None, All, TopLevel(顶级函数，不包括在类中的函数),

# AllDefinitions(所有的定义，不包括声明), TopLevelDefinitions(所有的顶级函数的定义)
AlwaysBreakAfterReturnType: None

# 总是在多行string字面量前换行
AlwaysBreakBeforeMultilineStrings: false

# 总是在template声明后换行
AlwaysBreakTemplateDeclarations: false

# false表示函数实参要么都在同一行，要么都各自一行
BinPackArguments: true

# false表示所有形参要么都在同一行，要么都各自一行
BinPackParameters: true

# 大括号换行，只有当BreakBeforeBraces设置为Custom时才有效
BraceWrapping:

# class定义后面
  AfterClass: false

# 控制语句后面
  AfterControlStatement: false

# enum定义后面
  AfterEnum: false

# 函数定义后面
  AfterFunction: false

# 命名空间定义后面
  AfterNamespace: false

# ObjC定义后面
  AfterObjCDeclaration: false

# struct定义后面
  AfterStruct: false

# union定义后面
  AfterUnion: false

# catch之前
  BeforeCatch: true

# else之前
  BeforeElse: true

# 缩进大括号
  IndentBraces: false

# 在二元运算符前换行: None(在操作符后换行), NonAssignment(在非赋值的操作符前换行), All(在操作符前换行)
BreakBeforeBinaryOperators: NonAssignment

# 在大括号前换行: Attach(始终将大括号附加到周围的上下文), Linux(除函数、命名空间和类定义，与Attach类似),

#   Mozilla(除枚举、函数、记录定义，与Attach类似), Stroustrup(除函数定义、catch、else，与Attach类似),

#   Allman(总是在大括号前换行), GNU(总是在大括号前换行，并对于控制语句的大括号增加额外的缩进), WebKit(在函数前换行), Custom 如果不换行岂不是一直出屏幕外了？

#   注：这里认为语句块也属于函数
BreakBeforeBraces: Custom

# 在三元运算符前换行
BreakBeforeTernaryOperators: true

# 在构造函数的初始化列表的逗号前换行
BreakConstructorInitializersBeforeComma: false

# 每行字符的限制, 0表示没有限制
ColumnLimit: 80

# 描述具有特殊意义的注释的正则表达式, 它不应该被分割为多行或以其它方式改变
CommentPragmas: '^ IWYU pragma:'

# 构造函数的初始化列表要么都在同一行, 要么都各自一行
ConstructorInitializerAllOnOneLineOrOnePerLine: true

# 构造函数的初始化列表的缩进宽度
ConstructorInitializerIndentWidth: 4

# 延续的行的缩进宽度
ContinuationIndentWidth: 4

# 去除C++11的列表初始化的大括号{后和}前的空格
Cpp11BracedListStyle: false

# 继承最常用的指针和引用的对齐方式
DerivePointerAlignment: false

# 关闭格式化
DisableFormat: false

# 自动检测函数的调用和定义是否被格式为每行一个参数(Experimental)
ExperimentalAutoDetectBinPacking: false

# 需要被解读为foreach循环而不是函数调用的宏
ForEachMacros: [ foreach, Q_FOREACH, BOOST_FOREACH ]

# 对
#include进行排序, 匹配了某正则表达式的
#include拥有对应的优先级, 匹配不到的则默认优先级为INT_MAX(优先级越小排序越靠前),

#   可以定义负数优先级从而保证某些
#include永远在最前面
IncludeCategories:
  - Regex: '^"(llvm|llvm-c|clang|clang-c)/'
    Priority: 2
  - Regex: '^(<|"(gtest|isl|json)/)'
    Priority: 3
  - Regex: '.*'
    Priority: 1

# 缩进case标签
IndentCaseLabels: false

# 缩进宽度
IndentWidth: 4

# 函数返回类型换行时, 缩进函数声明或函数定义的函数名
IndentWrappedFunctionNames: false

# 保留在块开始处的空行
KeepEmptyLinesAtTheStartOfBlocks: true

# 开始一个块的宏的正则表达式
MacroBlockBegin: ''

# 结束一个块的宏的正则表达式
MacroBlockEnd: ''

# 连续空行的最大数量
MaxEmptyLinesToKeep: 2

# 命名空间的缩进: None, Inner(缩进嵌套的命名空间中的内容), All
NamespaceIndentation: Inner

# 使用ObjC块时缩进宽度
ObjCBlockIndentWidth: 4

# 在ObjC的@property后添加一个空格
ObjCSpaceAfterProperty: false

# 在ObjC的protocol列表前添加一个空格
ObjCSpaceBeforeProtocolList: true

# 在call(后对函数调用换行的penalty
PenaltyBreakBeforeFirstCallParameter: 19

# 在一个注释中引入换行的penalty
PenaltyBreakComment: 300

# 第一次在 << 前换行的penalty
PenaltyBreakFirstLessLess: 120

# 在一个字符串字面量中引入换行的penalty
PenaltyBreakString: 1000

# 对于每个在行字符数限制之外的字符的penalty
PenaltyExcessCharacter: 1000000

# 将函数的返回类型放到它自己的行的penalty
PenaltyReturnTypeOnItsOwnLine: 60

# 指针和引用的对齐: Left, Right, Middle
PointerAlignment: Left

# 允许重新排版注释
ReflowComments: true

# 允许排序
#include
SortIncludes: true

# 在C风格类型转换后添加空格
SpaceAfterCStyleCast: false

# 在赋值运算符之前添加空格
SpaceBeforeAssignmentOperators: true

# 开圆括号之前添加一个空格: Never, ControlStatements, Always
SpaceBeforeParens: ControlStatements

# 在空的圆括号中添加空格
SpaceInEmptyParentheses: false

# 在尾随的评论前添加的空格数(只适用于//)
SpacesBeforeTrailingComments: 2

# 在尖括号的 < 后和 > 前添加空格
SpacesInAngles: true

# 在容器(ObjC和JavaScript的数组和字典等)字面量中添加空格
SpacesInContainerLiterals: true

# 在C风格类型转换的括号中添加空格
SpacesInCStyleCastParentheses: true

# 在圆括号的(后和)前添加空格
SpacesInParentheses: true

# 在方括号的[后和]前添加空格, lamda表达式和未指明大小的数组的声明不受影响
SpacesInSquareBrackets: false

# 标准: Cpp03, Cpp11, Auto
Standard: Cpp11

# tab宽度
TabWidth: 4

# 使用tab字符: Never, ForIndentation, ForContinuationAndIndentation, Always
UseTab: Never