https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80721
Bug ID: 80721
Summary: Sorting/Merging of free EH-emergency buffer may wrong
or uncomplete
Product: gcc
Version: 6.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: meisenmann....@fh-salzburg.ac.at
Target Milestone: ---
Created attachment 41345
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41345&action=edit
Suggested patch to fix order/fragmentation-issue in EH-emergency free-list
Hi!
My following findings describing "only" a minor issue and I'm not sure, whether
this can occur in "real life" or it's important (because, it's for a low-memory
situation):
If EH-emergency buffer are not free in reverse order of allocation, the order
of the free-list may wrong or not all possible merges are processed.
a) If the free-list is empty or the block to free is directly right of the
first item, this free-block is put as head (maybe after merge).
But, if the free-block is left to the first item and not merge-able, it is
sorted/put in as second item (instead of new first head).
b) If a block (to free) has a direct left free-block, it is merged into this;
but there's no check/merge to a direct following right free-block
[-> sub-optimal "fragmentation" within the free list].
IMHO, I will provide a suggested patch (with refactoring/simplification ...
... free to be used, if you are also see this as issue).
Best regards from Salzburg,
Marks
