Why only the constant expression can be used as case expression in Switch statement?

Posted by sinec on Stack Overflow See other posts from Stack Overflow or by sinec
Published on 2010-04-16T11:48:30Z Indexed on 2010/04/16 11:53 UTC
Read the original article Hit count: 225

Filed under:

c++

|

compiler

|

switch-statement

Hi,

what is bothering me is that I can't found an info regarding the question from the title.

I found that assembly form the Switch-case statement is compiled into bunch of (MS VC 2008 compiler) cmp and je calls:

0041250C  mov         eax,dword ptr [i] 
0041250F  mov         dword ptr [ebp-100h],eax 
00412515  cmp         dword ptr [ebp-100h],1 
0041251C  je          wmain+52h (412532h) 
0041251E  cmp         dword ptr [ebp-100h],2 
00412525  je          wmain+5Bh (41253Bh) 
00412527  cmp         dword ptr [ebp-100h],3 
0041252E  je          wmain+64h (412544h) 
00412530  jmp         wmain+6Bh (41254Bh)

where for above code will in case that if condition (i) is equal to 2, jump to address 41253Bh and do execution form there (at 41253Bh starts the code for 'case 2:' block)

What I don't understand is why in case that,for instance, function is used as 'case expression', why first function couldn't be evaluated and then its result compared with the condition?

Am I missing something?

Thank you in advance

© Stack Overflow or respective owner

Related posts about c++

Which C++ book shold I get between "C++ Primer" vs "C++ Primer Plus"

as seen on Stack Overflow - Search for 'Stack Overflow'
I want to learn C++ by using Vim and MinGW as compiler. I'm interesting at "C++ Primer (4th Edition)" and "C++ Primer Plus (5th Edition)" but I don't know how about it different. It has no book store that I can review those books, so I want to know, what is the different between those book and which… >>> More
C++ : C++ Primer (Stanley Lipmann) or The C++ programming language (special edition)

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a Computer Science degree (long2 time ago) .. I do know Java OOP but i am now trying to pick up C++. I do have C and of course data structure using C or pascal. I have started reading Bjarne Stroustrup book (The C++ Programming Language - Special Edition) but find it extremely difficult esp… >>> More
I need help on my C++ assignment using MS Visual C++

as seen on Stack Overflow - Search for 'Stack Overflow'
Ok, so I don't want you to do my homework for me, but I'm a little lost with this final assignment and need all the help I can get. Learning about programming is tough enough, but doing it online is next to impossible for me... Now, to get to the program, I am going to paste what I have so far. This… >>> More
Managed c++ std::string not accessible in unmanaged c++

as seen on Stack Overflow - Search for 'Stack Overflow'
In unmanaged c++ dll i have a function which takes constant std::string as argument Prototype : void read ( const std::string &imageSpec_ ) I call this function from managed c++ dll by passing a std::string. When i debug the unmanaged c++ code the parameter imageSpec_ shows the value correctly… >>> More
The Definitive C++ Book Guide and List

as seen on Stack Overflow - Search for 'Stack Overflow'
After more than a few questions about deciding on C++ books I thought we could make a better community wiki version. Providing QUALITY books and an approximate skill level. Maybe we can add a short blurb/description about each book that you have personally read / benefited from. Feel free to debate… >>> More

Related posts about compiler

IDEA modular problem (jsp)

as seen on Stack Overflow - Search for 'Stack Overflow'
I have project in with 2 separate modules(frontend and backend, first depends on second). When I'm trying to access backend code from frontend code, things going fine. Things turn for the worse when I do the same from jsp. This is stacktrase for simple accessign bean <jsp:useBean id="mybean"… >>> More
Help with a compiler warning: Initialization from distinct Objective-C type when types match

as seen on Stack Overflow - Search for 'Stack Overflow'
Here is the function where I get the compiler warning, I can't seem to figure out what is causing it. Any help is appreciated. -(void)displaySelector{ //warning on the following line: InstanceSelectorViewController *controller = [[InstanceSelectorViewController alloc] initWithCreator:self]; … >>> More
Sometimes Java web app hang

as seen on Stack Overflow - Search for 'Stack Overflow'
The web app occasionally get hang for about 30 seconds when user request a web page, the server's CPU and memory usage are ok, and the jstack shows: "http-9999-3" daemon prio=6 tid=0x552f3400 nid=0xf40 runnable [0x578fc000] java.lang.Thread.State: RUNNABLE at org.eclipse.jdt.internal.compiler… >>> More
Need help regarding one LALR(1) parsing.

as seen on Stack Overflow - Search for 'Stack Overflow'
I am trying to parse a context-free language, called Context Free Art. I have created its parser in Javascript using a YACC-like JS LALR(1) parser generator JSCC. Take the example of following CFA (Context Free Art) code. This code is a valid CFA. startshape A rule A { CIRCLE { s 1} } Notice the… >>> More
Port Compiler Options (8 replies)

as seen on .NET 247 - Search for '.NET 247'
I currently own a license for Crossworks for ARM and would like to compile the port using it. With the code for the CLR now available, is it possible to compile the port with any ARM compiler or are we still restricted to the Keil ARM gcc compilers? >>> More