Author: Chris lattner
Original: http://blog.llvm.org/2011/05/what-every-c-programmer-should-know.html
Sometimes, people may ask why the Code Compiled by llvm sometimes generates sigtrap signals when the optimizer is turned on. After in-depth analysis, they found that clang generated a "ud2" command (assuming x86 code) -- the same as _ builtin_trap. Here there are several questions, all about the undefined behavior in the C code and how llvm handles it
above, it will mess up my build log.
The deprecated-declarations warning should be ignored. You can see the preceding clang error output.
([-Wdeprecated-declarations] indicates the error type because the deprecated-delcarations option is enabled ). In addition, you can know which class generates a warning-this is why I prefer clang more. If it is GCC, you will not get any useful messages.
By setting the-wn
the control.
E,UIControlEventTouchDragEnter
It refers to the event generated during the drag action from outside the control boundary to the inner.
F,UIControlEventTouchDragExit
An event generated when the widget is dragged from inside to outside the control boundary.
G,UIControlEventTouchUpInside
When the mouse is raised within the control range, you must first press, that isUIControlEventTouchDownOrUIControlEventTouchDownRepeatEvent.
H,UIControlEventTouchUpOutside
When you move the cursor out
Let's talk about Objective-C warnings and objective-c.
Address: http://onevcat.com/2013/05/talk-about-warning/
A programmer with exercises cares about the warning of his own code, just like a dead cockroach on the side of the rice bowl. -- @ OnevcatCompilation warning
Now the compiler is sometimes very noisy, and the warning given by the compiler is very useful to developers. The warning will not stop compilation and linking, nor cause the program to be unable to run, but many times the compile
Research tools
Clang in order to study the compiler implementation principle, we need to use the clang command. The clang command can be used to rewrite the source code of the objetive-c into C + + language, which can be used to study the source code implementation of each feature in block.
CLANG-RE
ObjectiveIt is believed that most developers who have seen @weakify and @strongify will love the two macros. But many people only know the power of it, but do not realize the danger in a particular environment.This article will tell the reader how to use these two macros correctly by means of code testing.@weakify and @strongify
This article is intended to illustrate its dangers, so the two macros will not be fully explained.If you are interested in it, please refer to other authors ' a
Used in the past is the way of CTAGS+OMNICOMPLETE+ACP, this time replaced by clang self-analytic way to try a.Ever since I knew Vundle, my mother never had to worry about me getting into trouble with the underground plugin.0. Install the necessary componentssudo apt-get install Libncurses5-dev libgnome2-dev libgnomeui-Dev libgtk2. 0-dev libatk1. 0-dev libbonoboui2-Dev libcairo2-dev libx11-dev libxpm-dev libxt-dev python-dev Ruby-dev Mercur
LLVM is a very powerful compiler, the specific content of the reader's own Baidu a bitInstallation steps:1. Installing LLVM2. Install Python's llvmlite packageI. Installing the LLVM (version 3.5)1. Required DocumentsLLVM Source CodeClang Source CodeClang Tools Extra Source codeCompiler RT Source CodeLibc++ Source CodeAbove these files in this link: http://llvm.org/releases/download.html#3.5 after the download , four compressed packets are extracted, get four directories:Llvm-3.5.srcCfe-3.5.srcC
component build project!The error message shows that the Llvm-ar command could not be found.Run the command clang--version , confirming that LLVM 3.5 is installed:Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5SVN)Run command ls/usr/bin/llvm* , indeed no Llvm-ar:/usr/bin/llvm-g++/usr/bin/llvm-gccLater found that the original hidden in the /usr/local/opt/llvm/bin/folder:Ls/usr/local/opt/llvm/bin/
diagnostic information that includes the type of information.Run-time outputUsing the printf method (not that I recommend you to use printf) the display type information cannot be used at run time, but it requires full control over the output format, and the difficulty is how to make the type of the variable behave reasonably in the form of text, and you may feel "no problem" typeID and std:: Type_info will solve this problem, you think we can write down the following code to know the types of
Instrumentation Pass works by examining all "alloca" instructions in the intermediate representatio N (IR) of a function (clang the code into LLVM's intermediate representation and later, after various InStr Umentation/optimization passes, translates the IR into machine code). An "alloca" instruction allocates spaces on the stack for a local variable or array. The Safestack instrumentation Pass then traverses the "list of instructions" make use of th
Python built-in functions (12) -- compile, pythoncompile
English document:
compile(Source,Filename,Mode,Flags = 0,Dont_inherit = False,Optimize =-1)
Compile
SourceInto a code or AST object. Code objects can be executed
exec()Or
eval().
SourceCan either be a normal string, a byte string, or an AST object. Refer to
astModule documentation for information on how to work with
We all know the PHP script execution process, first by the Zend engine to compile the PHP source code into a opcode sequence, and then by the Zend VM to explain the execution. The general compilation process is the first lexical analysis, syntax analysis, and then the compilation. After parsing, there is the concept of an abstract syntax tree (abstractsyntax tree or abbreviated AST), which is the output of the parsing, and then the compiler is based o
recursion. That's what I do. However, the parser is not that simple, and it produces another problem: when left recursion correctly parses 3-2-1 as (3-2)-1, the right recursion is incorrectly parsed as 3-(2-1 ). I didn't think of a simple solution, so in order to make things simple, I decided to let it continue to use the wrong parsing format and handle the problem later (see step 4)
Step 3: Resolve to an AST
The algorithm is actually very simple. We
:/\+|-|\*|\/|%| ===|\!==|==|\!=|
Four, $parse syntax parser
1. The conceptAst:abstract Syntax tree, abstract syntax treesAbstract syntax trees (abstract Syntax tree, AST), as an intermediate representation of programs, are widely used in many fields such as program analysis. The use of abstract syntax tree can easily implement a variety of source program processing tools, such as source program browser, intelligent editor, language translator and so o
, such as ANTLR, could not escape the problem, and it would replace infinite recursion with friendly error prompts, unlike our toy parser.
Left recursion can be easily converted to right recursion, as I do. But the parser is not that simple, and it creates another problem: when the left recursive correct parsing 3-2-1 is (3-2)-1, and the right recursion is incorrectly resolved to 3-(2-1). I haven't thought of a simple solution, so in order to make things simple, I decided to let it continue usi
:
In fact, the role of the Babel plugin is to import { equal } from 'diana' compile import equal from 'diana/lib/equal' .Babel plug-in execution mechanism
The Babel execution trilogy is as follows:
Analytical
Using Babel-parse to parse the JS code into an AST tree
Transformation
The AST tree is traversed with babel-traverse, and the Babel-core is used to transform invoke the corre
. Framework Initialization
First, initialize the analysis framework, mainly collecting information about all user-defined classes in the source code project to be analyzed, including class names, class attributes, class method names, the file path of the class.
These records are stored in the Context class of the global Context class, which is designed in the singleton mode and resident memory for later analysis.
2. Judge the Main File
Next, determine whether each PHP file is a Main file. In PHP
-up (bottom-up) that it mentions. So my DSL is probably divided into two parts:
Generate AST (Abstract syntax tree
Extract groups by priority (parentheses) from low to high, staging to grouped data
Grouping branches by (and/or) logical gates, generating a syntax tree AST
Iterate through the AST from top to bottom to restore and rep
obvious. We can use a number conversion technique: 14 .. toString (15) + 31 .. toString (32) + 0xf1. toString (22 );
If you do not do anything, expand the number: (0b1110 ). toString (4
Final effect: window [(2*7 ). toString (4
Many such reciprocal operations can be found in js. By using a random generation method to combine them, simple expressions can be infinitely complicated.0x02 static analysis implementation
Parse and transform code
In this article, the idea of implementing anti-obfusca
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