pragma | 易学教程

What is the use of pragma code section and data section?

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问题 What exactly will happen to the data segment and text segment if I use the below two lines in my c source code file? #pragma CODE_SECTION(func1, "Sec1") #pragma DATA_SECTION(globalvar1, "Sec2") 回答1: Source (contains examples): http://hi.baidu.com/jevidyang/blog/item/6d4dc436d87e3a300b55a918.html Note: #pragma is compiler specific, so syntax may vary for your compiler. The DATA_SECTION pragma allocates space for the symbol in a section called section name. The syntax for the pragma in C could

Trouble disabling LLVM optimizations via pragma

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问题 I have a chunk of code that crashes unless I build with optimizations off. I'm building with LLVM compiler 2.0 I would like to turn off optimizations by wrapping the offending code with a #pragma compiler directive; or turn off optimizations for an entire file. I've been digging in the clang manual and code; but nothing jumps out at me. Does anyone know how to change the optimizations for a single CU (as opposed to for the entire app)? 回答1: You can set per-file compiler flags in Xcode. In

Why isn't #pragma once automatically assumed?

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问题 What's the point of telling the compiler specifically to include the file only once? Wouldn't it make sense by default? Is there even any reason to include a single file multiple times? Why not just assume it? Is it to do with specific hardware? 回答1: There are multiple related questions here: Why is #pragma once not automatically enforced? Because there are situations in which you want to include files more than once. Why would you want to include a file multiple times? Several reasons have

What is the difference between parent and base in Perl 5?

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问题 There appears to be a new pragma named parent that does roughly the same thing as base. What does parent do that warrants a new (non-core) module? I am missing something? 回答1: base tried to do one too many things – automatically handling loading modules but also allowing establishing inheritance from classes already loaded (possibly from a file whose name wasn't based on the module name). To sort of make it work, there was some hackery that caused surprising results in some cases. Rather than

How to silence a warning in swift

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I have a piece of code which is generating lots of warnings (deprecated API) Using clang* I could do #pragma clang diagnostic push #pragma clang diagnostic ignored "-Wdeprecated-declarations" ... #pragma clang diagnostic pop However this does not work in swift. How to do it in swift ? Note: I don't want to disable the warning globally, nor even file wide, but just disable a specific warning in a specific part of my source code. Edit: I looks like my note was not clear enough: I do NOT want conditional compilation (which is the proposed answer of the supposed duplicate). I just want to silence

How do I use sqlite3 PRAGMA user_version in Objective-c?

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问题 I am trying to check the user_version of the sqlite DB. I have an admin tool to bump the version, but I don't understand the syntax of the pragma statement. I am expecting to test the value in an if-statement. Can someone provide a code sample? When I embed the pragma statement in my objective-c code, the compiler throws an error. 回答1: I figured it out with the inspiration from newtover, digging into FMDB and re-reading the sqlite3 documentation (it is still very vague in my opinion). This

Is there a way to disable all warnings with a pragma?

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问题 I've started a new project and have decided to make sure it builds cleanly with the /Wall option enabled. The only problem is not all 3rd party libraries (like boost) compile without warnings, so I've resorted to doing this in a shared header: #pragma warning(push) #pragma warning(disable:4820) #pragma warning(disable:4619) #pragma warning(disable:4668) #pragma warning(disable:4625) #pragma warning(disable:4626) #pragma warning(disable:4571) #pragma warning(disable:4347) #pragma warning

Where does the word “pragma” come from?

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问题 So I know what pragma is, and what it's used for, but what is the meaning of the word itself? I've used it many times in code, but I never really knew what the word actually means or stands for. 回答1: According to a US Government-owned(!) document describing the design of Ada: Rationale for the Design of the Ada® Programming Language : A pragma (from the Greek word meaning action) is used to direct the actions of the compiler in particular ways, but has no effect on the semantics of a program

C#: Is pragma warning restore needed?

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问题 From msdn I get this: #pragma warning disable warning-list #pragma warning restore warning-list In the examples, both disable and restore are used. Is it necessary to restore if I want it disabled for a whole file? Like, if I do not restore, how far does it carry? Are the warnings disabled for everything compiled after that? Or just for the rest of that file? Or is it ignored? 回答1: If you do not restore the disabling is active for the remainder of the file. Interestingly this behaviour is not

What does “#pragma comment” mean?

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What does #pragma comment mean in the following? #pragma comment(lib, "kernel32") #pragma comment(lib, "user32") #pragma comment is a compiler directive which indicates Visual C++ to leave a comment in the generated object file. The comment can then be read by the linker when it processes object files. #pragma comment(lib, libname) tells the linker to add the 'libname' library to the list of library dependencies, as if you had added it in the project properties at Linker->Input->Additional dependencies See #pragma comment on MSDN JustBoo I've always called them "compiler directives." They