C Programming Language :: Changing the execution path of methods at runtime


	Home \| .Net Programming \| cSharp Home \| Sql Server Home \| Javascript / Client Side Development \| Ajax Programming Ruby on Rails Development \| Perl Programming \| C Programming Language \| C++ Programming \| IT Jobs Python Programming Language \| Laptop Suggestions? \| TCL Scripting \| Fortran Programming \| Scheme Programming Language

Cervo Technologies
The Right Source to Outsource

MS Dynamics CRM 3.0


	C Programming Language


	Changing the execution path of methods at runtime Hi All, Can i change the execution path of methods in my process at runtime? e.g a()->b()->c()->d()->e() Now, i want execution to be altered at runtime as - a()->b()->myfun1()->myfun2()->myfun3()... ->e() Can this be done without changing the actual source file, may be by adding a new module at runtime? Thanks --pradeep In article <1180449520.473891.53@q19g2000prn.googlegroups.com>, blufox <2500.prad@gmail.com> wrote: >Can i change the execution path of methods in my process at runtime? Not in C, because C does not have methods. >e.g >a()->b()->c()->d()->e() >Now, i want execution to be altered at runtime as - >a()->b()->myfun1()->myfun2()->myfun3()... ->e() >Can this be done without changing the actual source file, may be by >adding a new module at runtime? C does not have modules either. Furthermore, C does not offer any method of activating new code at runtime. Some operating systems provide mechanisms for dynamically loadable objects. In the Windows world, these are usually called 'dll'; in the Unix world, these are usually called 'dso' but the Unix operating system calls usually begin with dlopen() . -- Okay, buzzwords only. Two syllables, tops. -- Laurie Anderson On May 29, 7:43 pm, rober@ibd.nrc-cnrc.gc.ca (Walter Roberson) wrote: > In article <1180449520.473891.53@q19g2000prn.googlegroups.com>, > blufox <2500.prad@gmail.com> wrote: > >Can i change the execution path of methods in my process at runtime? > Not in C, because C does not have methods. Right. Apologies i meant kernel functions in linux which are usually called methods. > >e.g > >a()->b()->c()->d()->e() > >Now, i want execution to be altered at runtime as - > >a()->b()->myfun1()->myfun2()->myfun3()... ->e() > >Can this be done without changing the actual source file, may be by > >adding a new module at runtime? > C does not have modules either. Furthermore, C does not offer any > method of activating new code at runtime. > Some operating systems provide mechanisms for dynamically loadable > objects. In the Windows world, these are usually called 'dll'; > in the Unix world, these are usually called 'dso' but the > Unix operating system calls usually begin with dlopen() . Right, and i mean a Linux kernel module here. Essentially it is C(with loads of GCCism) i guess. So, is it possible using modules in unix/linux then. i must ask? Thanks for the reply --pradeep - Hide quoted text - > -- > Okay, buzzwords only. Two syllables, tops. -- Laurie Anderson - Hide quoted text - blufox wrote: > Hi All, > Can i change the execution path of methods in my process at runtime? > e.g > a()->b()->c()->d()->e() > Now, i want execution to be altered at runtime as - > a()->b()->myfun1()->myfun2()->myfun3()... ->e() > Can this be done without changing the actual source file, may be by > adding a new module at runtime? > Thanks > --pradeep Hi a()->b()->c()->d()->e() means (in C): call function a(), that returns some pointer to a structure that has a field called "b". This field is a function pointer. Call that, and that will return some structure with a field "c". That field is a function pointer... etc Note that the type of the return of a() is known at compile time. The compiler has then calculated at which offset the "b" pointer is, and generates code to access that pointer at that offset. You can't change that. You can only change the value in the field "b", in the structure returned by a(). If a returns the same structure but with a function pointer to "myfun", the generated code will work the same, but you will end calling another function, not the one that you were calling This requires a modification at compile time to a() or to b(), etc. Somehow those functions will need to figure out when they should put a certain function pointer in field "b" or not. But all this looks far too complicated. WHAT are you trying to do? Explain that first. jacob On May 29, 8:01 pm, jacob navia <j@jacob.remcomp.fr> wrote: - Hide quoted text - > blufox wrote: > > Hi All, > > Can i change the execution path of methods in my process at runtime? > > e.g > > a()->b()->c()->d()->e() > > Now, i want execution to be altered at runtime as - > > a()->b()->myfun1()->myfun2()->myfun3()... ->e() > > Can this be done without changing the actual source file, may be by > > adding a new module at runtime? > > Thanks > > --pradeep > Hi > a()->b()->c()->d()->e() > means (in C): > call function a(), that returns some pointer to a > structure that has a field called "b". This field is a function > pointer. Call that, and that will return some structure with > a field "c". That field is a function pointer... > etc > Note that the type of the return of a() is known at compile > time. The compiler has then calculated at which offset the "b" > pointer is, and generates code to access that pointer at that > offset. You can't change that. You can only change the value > in the field "b", in the structure returned by a(). > If a returns the same structure but with a function pointer to > "myfun", the generated code will work the same, but you will > end calling another function, not the one that you were calling > This requires a modification at compile time to a() or to b(), etc. > Somehow those functions will need to figure out when they should put > a certain function pointer in field "b" or not. > But all this looks far too complicated. > WHAT are you trying to do? > Explain that first. Oops i messed it up i must admit. :-( No it is not pointer dereferencing literally here. Just to illustrate the flow of program here, i used arrows "->" . What I intend to do? I want to invoke my function without changing the actual source code at runtime. Is this somehow possible on a Linux system? Thanks --pradeep - Hide quoted text - > jacob On May 29, 4:07 pm, blufox <2500.prad@gmail.com> wrote: - Hide quoted text - > On May 29, 8:01 pm, jacob navia <j@jacob.remcomp.fr> wrote: > > blufox wrote: > > > Hi All, > > > Can i change the execution path of methods in my process at runtime? > > > e.g > > > a()->b()->c()->d()->e() > > > Now, i want execution to be altered at runtime as - > > > a()->b()->myfun1()->myfun2()->myfun3()... ->e() > > > Can this be done without changing the actual source file, may be by > > > adding a new module at runtime? > > > Thanks > > > --pradeep > > Hi > > a()->b()->c()->d()->e() > > means (in C): > > call function a(), that returns some pointer to a > > structure that has a field called "b". This field is a function > > pointer. Call that, and that will return some structure with > > a field "c". That field is a function pointer... > > etc > > Note that the type of the return of a() is known at compile > > time. The compiler has then calculated at which offset the "b" > > pointer is, and generates code to access that pointer at that > > offset. You can't change that. You can only change the value > > in the field "b", in the structure returned by a(). > > If a returns the same structure but with a function pointer to > > "myfun", the generated code will work the same, but you will > > end calling another function, not the one that you were calling > > This requires a modification at compile time to a() or to b(), etc. > > Somehow those functions will need to figure out when they should put > > a certain function pointer in field "b" or not. > > But all this looks far too complicated. > > WHAT are you trying to do? > > Explain that first. > Oops i messed it up i must admit. :-( > No it is not pointer dereferencing literally here. > Just to illustrate the flow of program here, i used arrows "->" . > What I intend to do? > I want to invoke my function without changing the actual source code > at runtime. > Is this somehow possible on a Linux system? > Thanks > --pradeep > > jacob It's just about possible using portable C, but only if you design the source file to make it possible. For instance: /* whichfunc.c / extern void c(void); extern void myfun1(void); void (func)()=c; /* =myfun1; / / prog.c / extern void (func)(); void a(void) { b(); } void b(void) { (func)(); / the key line / } / ... whatever ... / Then you can link both files together using whatever implementation- specific method your implementation provides (if you're on Linux, you're quite possibly using gcc, in which case you specify both files on the command line or probably use a makefile if it's a complex project). Changing func will change the path of execution b takes. Of course, modifying the source code is nearly always going to be easier (the only advantage of doing it like this is that you can change the flow pattern at runtime if you want to, by assigning to func). In the general case, in which you haven't deliberately written the source code in this unusual form, you can't substitute a call to one function with another using what's available in standard C89/C99. -- ais523 blufox <2500.prad@gmail.com> writes: > On May 29, 7:43 pm, rober@ibd.nrc-cnrc.gc.ca (Walter Roberson) > wrote: >> In article <1180449520.473891.53@q19g2000prn.googlegroups.com>, >> blufox <2500.prad@gmail.com> wrote: >> >Can i change the execution path of methods in my process at runtime? >> Not in C, because C does not have methods. > Right. Apologies i meant kernel functions in linux which are usually > called methods. They are? That's news to me. In any case, you should ask on a Linux-specific newsgroup. -- Keith Thompson (The_Other_Keith) k@mib.org <http://www.ghoti.net/~kst> San Diego Supercomputer Center <> <http://users.sdsc.edu/~kst> "We must do something. This is something. Therefore, we must do this." -- Antony Jay and Jonathan Lynn, "Yes Minister" On May 30, 3:00 am, Keith Thompson <k@mib.org> wrote: > blufox <2500.prad@gmail.com> writes: > > On May 29, 7:43 pm, rober@ibd.nrc-cnrc.gc.ca (Walter Roberson) > > wrote: > >> In article <1180449520.473891.53@q19g2000prn.googlegroups.com>, > >> blufox <2500.prad@gmail.com> wrote: > >> >Can i change the execution path of methods in my process at runtime? > >> Not in C, because C does not have methods. > > Right. Apologies i meant kernel functions in linux which are usually > > called methods. > They are? That's news to me. Yes they are called methods in the kernel AFAIK. May be i am misunderstanding it. > In any case, you should ask on a Linux-specific newsgroup. Tried that, didn't get satisfying answers so resorted to clc. I 'll give another try though. Thank you --psr - Hide quoted text - > -- > Keith Thompson (The_Other_Keith) k@mib.org <http://www.ghoti.net/~kst> > San Diego Supercomputer Center <> <http://users.sdsc.edu/~kst> > "We must do something. This is something. Therefore, we must do this." > -- Antony Jay and Jonathan Lynn, "Yes Minister" On May 29, 8:30 pm, ais523 <ais@bham.ac.uk> wrote: - Hide quoted text - > On May 29, 4:07 pm, blufox <2500.prad@gmail.com> wrote: > > On May 29, 8:01 pm, jacob navia <j@jacob.remcomp.fr> wrote: > > > blufox wrote: > > > > Hi All, > > > > Can i change the execution path of methods in my process at runtime? > > > > e.g > > > > a()->b()->c()->d()->e() > > > > Now, i want execution to be altered at runtime as - > > > > a()->b()->myfun1()->myfun2()->myfun3()... ->e() > > > > Can this be done without changing the actual source file, may be by > > > > adding a new module at runtime? > > > > Thanks > > > > --pradeep > > > Hi > > > a()->b()->c()->d()->e() > > > means (in C): > > > call function a(), that returns some pointer to a > > > structure that has a field called "b". This field is a function > > > pointer. Call that, and that will return some structure with > > > a field "c". That field is a function pointer... > > > etc > > > Note that the type of the return of a() is known at compile > > > time. The compiler has then calculated at which offset the "b" > > > pointer is, and generates code to access that pointer at that > > > offset. You can't change that. You can only change the value > > > in the field "b", in the structure returned by a(). > > > If a returns the same structure but with a function pointer to > > > "myfun", the generated code will work the same, but you will > > > end calling another function, not the one that you were calling > > > This requires a modification at compile time to a() or to b(), etc. > > > Somehow those functions will need to figure out when they should put > > > a certain function pointer in field "b" or not. > > > But all this looks far too complicated. > > > WHAT are you trying to do? > > > Explain that first. > > Oops i messed it up i must admit. :-( > > No it is not pointer dereferencing literally here. > > Just to illustrate the flow of program here, i used arrows "->" . > > What I intend to do? > > I want to invoke my function without changing the actual source code > > at runtime. > > Is this somehow possible on a Linux system? > > Thanks > > --pradeep > > > jacob > It's just about possible using portable C, but only if you design the > source file to make it possible. For instance: > / whichfunc.c / > extern void c(void); > extern void myfun1(void); > void (func)()=c; /* =myfun1; / > / prog.c / > extern void (func)(); > void a(void) > { > b(); > } > void b(void) > { > (func)(); / the key line / > } > / ... whatever ... */ > Then you can link both files together using whatever implementation- > specific method your implementation provides (if you're on Linux, > you're quite possibly using gcc, in which case you specify both files > on the command line or probably use a makefile if it's a complex > project). Changing func will change the path of execution b takes. > Of course, modifying the source code is nearly always going to be > easier (the only advantage of doing it like this is that you can > change the flow pattern at runtime if you want to, by assigning to > func). > In the general case, in which you haven't deliberately written the > source code in this unusual form, you can't substitute a call to one > function with another using what's available in standard C89/C99. This is fruitful. I ll look into this and see if i can get something concrete from this hint. Thanks a ton for the help. --psr - Hide quoted text - > -- > ais523 blufox wrote: > ais523 <ais@bham.ac.uk> wrote: ... snip about 100 lines ... >> Of course, modifying the source code is nearly always going to be >> easier (the only advantage of doing it like this is that you can >> change the flow pattern at runtime if you want to, by assigning to >> func). >> In the general case, in which you haven't deliberately written the >> source code in this unusual form, you can't substitute a call to one >> function with another using what's available in standard C89/C99. > This is fruitful. I ll look into this and see if i can get something > concrete from this hint. Please snip irrelevant data from the quoted portion of your replies. The links below (in my sig) may be helpful. -- Some useful links on quoting: <http://www.xs4all.nl/%7ewijnands/nnq/nquote.html> <http://www.complang.tuwien.ac.at/anton/mail-news-errors.html> <http://www.netmeister.org/news/learn2quote2.html> <http://www.star-one.org.uk/computer/format.htm> -- Posted via a free Usenet account from http://www.teranews.com On 29 May 2007 20:42:00 -0700, in comp.lang.c , blufox <2500.prad@gmail.com> wrote: >On May 30, 3:00 am, Keith Thompson <k@mib.org> wrote: >> blufox <2500.prad@gmail.com> writes: >> > Right. Apologies i meant kernel functions in linux which are usually >> > called methods. >> They are? That's news to me. >Yes they are called methods in the kernel AFAIK. I've never heard anything called a method in C or C++. Some other languages such as VB and the ilk have methods. >May be i am misunderstanding it. Its possible... -- Mark McIntyre "Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it." --Brian Kernighan In article <5mvr53570pi03qamr05lmtfa5au3ck5@4ax.com>, Mark McIntyre <markmcint@spamcop.net> wrote: >On 29 May 2007 20:42:00 -0700, in comp.lang.c , blufox ><2500.prad@gmail.com> wrote: >>On May 30, 3:00 am, Keith Thompson <k@mib.org> wrote: >>> blufox <2500.prad@gmail.com> writes: >>> > Right. Apologies i meant kernel functions in linux which are usually >>> > called methods. >>> They are? That's news to me. >>Yes they are called methods in the kernel AFAIK. >I've never heard anything called a method in C or C++. Some other >languages such as VB and the ilk have methods. Of course you have (heard someone refer to C++ as having methods). That part of your statement (that "I've never heard...") is plain and simply a lie. The more substantive question is whether or not C++ has methods. Pretty clearly, it does (although of course this is all OT here), but I would imagine that you or one of your buddies will come up with some bit of sophistry to explain why it doesn't.


	Add to del.icio.us \| Digg this \| Stumble it \| Powered by Megasolutions Inc