Commit Larry Doolittle's buffers-on-stack/buffers-via-malloc patch.

-Erik
This commit is contained in:
Eric Andersen
2001-01-25 23:49:09 +00:00
parent ffde8673fe
commit d35c21587a
12 changed files with 51 additions and 28 deletions

View File

@@ -402,7 +402,7 @@ The problem with these is that any time any busybox app is run, you pay a
memory penalty for this buffer, even if the applet that uses said buffer is
not run. This can be fixed, thusly:
static char *buffer
static char *buffer;
...
other_func()
{
@@ -418,7 +418,7 @@ mallocing the buffers (and thus growing the text size), buffers can be
declared on the stack in the *_main() function and made available globally by
assigning them to a global pointer thusly:
static char *pbuffer
static char *pbuffer;
...
other_func()
{
@@ -430,13 +430,13 @@ assigning them to a global pointer thusly:
pbuffer = buffer; /* but available globally */
...
Thus:
- global static buffers are eliminated
- we don't grow the text segment as much because no malloc() call is made;
memory is automatically allocated on the stack when execution context
enters the function. (We still grow text a little bit because of the
assignment, but that's cheap compared to a function call.)
- the buffer is still available globally via the pointer
This last approach has some advantages (low code size, space not used until
it's needed), but can be a problem in some low resource machines that have
very limited stack space (e.g., uCLinux). busybox.h declares a macro that
implements compile-time selection between xmalloc() and stack creation, so
you can code the line in question as
RESERVE_BB_BUFFER(buffer, BUFSIZ);
and the right thing will happen, based on the customer's configuration.