@ Gene: Thanks for the nice explanation. Any pointers on where we can find such detailed explanation about compilation/compiler.
On Tue, Jul 13, 2010 at 6:25 PM, Ashish Goel <[email protected]> wrote: > the highest scope may not be true, it uses the current scope to chk if the > variable is defined there > any pointer to study material? > > Best Regards > Ashish Goel > "Think positive and find fuel in failure" > +919985813081 > +919966006652 > > > > On Wed, Jul 14, 2010 at 6:28 AM, Gene <[email protected]> wrote: > >> On Jul 8, 1:34 pm, gopinath sikha <[email protected]> wrote: >> > Hi guys, >> > >> > How gcc or any c compiler maintains the scope of the variable? >> > Especially all the static variable are maintained in the data section. >> > >> > Can anyone please respond. >> >> As a compiler processes the program, it maintains a table that maps >> identifier strings to associated attributes like type information, >> line number of declaration, etc., etc. This is called the symbol >> table. It's often implemented as a hash table. Self-balancing trees >> work fine, too. >> >> There are at least a couple of different ways to process scopes. Here >> is one. >> >> The symbol table must allow duplicate keys for this technique, so it's >> a multi-map rather than map. >> >> The compiler gives every scope a number. It does this by keeping a >> counter initialized at 0. Every time it sees a {, it increments the >> counter and the new value becomes the scope number. It also pushes >> each new scope number on a stack. At any given time, the stack >> contains the numbers of open scopes, with the innermost scope at the >> top. >> >> When the compiler processes a declaration, the declared name is added >> to the symbol table, and the scope number becomes one of its >> attributes. If an attempt is made to add a variable twice with the >> same scope number, a re-declaration error is printed for the user. >> >> When the compiler processes a variable use (as in x = 42), it looks up >> the variable (x) in the symbol table. If there is more than a single >> x, it uses the one with the highest scope number because this must be >> the "inner" scope where there is an x. If the variable (x) is not >> found at all, then an "undefined identifier" error is printed for the >> user. >> >> When the compiler processes the end of a scope, a }, it pops the scope >> stack. Say the closing scope is number N. Then the compiler removes >> all symbol table entries with scope N as attributes and keeps on >> processing. >> >> That's about it. There are some details like handling the id's for >> fields within structs, but I'm sure you can figure out how that works >> on your own. I.e. when you have struct point { float x, y; } x; x.x >> = 42; think about what the compiler is doing when it processes the >> { in the strut declaration, when it sees the x and the y, when it sees >> the second x and the third. >> >> Cheers. >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Algorithm Geeks" group. >> To post to this group, send email to [email protected]. >> To unsubscribe from this group, send email to >> [email protected]<algogeeks%[email protected]> >> . >> For more options, visit this group at >> http://groups.google.com/group/algogeeks?hl=en. >> >> > -- > You received this message because you are subscribed to the Google Groups > "Algorithm Geeks" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to > [email protected]<algogeeks%[email protected]> > . > For more options, visit this group at > http://groups.google.com/group/algogeeks?hl=en. > -- You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
