Talk:Path Manipulation

Hi,

Here is a problem I fought with a long time.

The directory you want to add to path must exist before you call AddToPath. If it doesn't exists the path environment variable doesn't change, and you get no error message.

/Pontus Bergendahl

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The stack manipulation in this article should be checked... I've always found it confusing to deal with, so I usually end up adding a lot of comments that keep track of the stack.

For the AddToEnvVar function, I end up with this:

      -- Beginning of function.  A and B are the ValueToAdd and EnvVarNames respectively --
             Stack: A B
 
Exch $1      Stack: 1 B
Exch         Stack: B 1
Exch $0      Stack: 0 1
Push $2      Stack: 2 0 1
Push $3      Stack: 3 2 0 1
Push $4      Stack: 4 3 2 0 1
 
      -- Put haystack (C) and needle (D) on stack --
Push "$2;"   Stack: C 4 3 2 0 1
Push "$1;"   Stack: D C 4 3 2 0 1
      -- StrStr is called, pops top two, pushes result (E) --
             Stack: E 4 3 2 0 1
Pop $3       Stack: 4 3 2 0 1
 
      -- Put haystack (C) and needle (D) on stack --
Push "$2;"   Stack: C 4 3 2 0 1
Push "$1\;"  Stack: D C 4 3 2 0 1
      -- StrStr is called, pops top two, pushes result (E) --
             Stack: E 4 3 2 0 1
Pop $3       Stack: 4 3 2 0 1
 
      -- IsNT is called, pushes result (F) --
             Stack: F 4 3 2 0 1
 
Pop $2       Stack: 4 3 2 0 1
Pop $4       Stack: 3 2 0 1
Pop $3       Stack: 2 0 1
Pop $2       Stack: 0 1
 
      -- The problem should be clear now --
 
Pop $1       Stack: 1 
Pop $0       Stack: -empty-

Let me know if I'm mistaken.. if not, the wiki should be edited (I'd do it now, but I want to be sure I didn't goof up, first)

You're correct. It seems the last two Pop commands are mixed. $0 should be popped first. The best test is setting $0-$9 with 0-9 (StrCpy $0 $$0, StrCpy $1 $$1, etc.) and checking them after the function returns. That test indeed shows they are mixed. Thanks, fixed. --kichik 14:03, 30 June 2006 (PDT)

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• why AddToPath is not calling AddToEnvVar, if they are equvalent? Mojo 05:05, 19 December 2006 (PST)
• i had problems with setting variables in installer and cleaning up in uninstaller, until i changed

  ;ReadEnvStr $2 $0
  ReadRegStr $2 ${WriteEnvStr_RegKey} $0

i think, function should read and write from/to one source. same for AddToPath. Mojo 05:05, 19 December 2006 (PST)

AddToEnvVar was added later by someone else.

Both functions already read from the registry key itself before writing the new value. They only check in the global value to make sure the value doesn't already exist. I don't see the problem with that.--kichik 04:12, 22 December 2006 (PST)

i had a problem, when install goes right after uninstall, ReadEnvStr reads some cached values, and goes to AddToPath_done label. i changed it to ReadRegStr which seems to read actual values. Mojo 06:12, 23 December 2006 (PST)

ReadEnvStr $1 PATH
Push "$1;"
Push "$0;"
Call StrStr
Pop $2
StrCmp $2 "" "" AddToPath_done

That's a very specific case. It happens because running processes don't update their environment. You should manually update as shown in Setting Environment Variables to Active Installer Process. Your alternative solution may miss variables defined elsewhere.