git/merge-ort.h
Elijah Newren 19ceb486f8 merge-ort: avoid accidental API mis-use
Previously, callers of the merge-ort API could have passed an
uninitialized value for struct merge_result *result.  However, we want
to check result to see if it has cached renames from a previous merge
that we can reuse; such values would be found behind result->priv.
However, if result->priv is uninitialized, attempting to access behind
it will give a segfault.  So, we need result->priv to be NULL (which
will be the case if the caller does a memset(&result, 0)), or be written
by a previous call to the merge-ort machinery.  Documenting this
requirement may help, but despite being the person who introduced this
requirement, I still missed it once and it did not fail in a very clear
way and led to a long debugging session.

Add a _properly_initialized field to merge_result; that value will be
0 if the caller zero'ed the merge_result, it will be set to a very
specific value by a previous run by the merge-ort machinery, and if it's
uninitialized it will most likely either be 0 or some value that does
not match the specific one we'd expect allowing us to throw a much more
meaningful error.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-05-20 15:40:39 +09:00

78 lines
2.3 KiB
C

#ifndef MERGE_ORT_H
#define MERGE_ORT_H
#include "merge-recursive.h"
struct commit;
struct tree;
struct merge_result {
/*
* Whether the merge is clean; possible values:
* 1: clean
* 0: not clean (merge conflicts)
* <0: operation aborted prematurely. (object database
* unreadable, disk full, etc.) Worktree may be left in an
* inconsistent state if operation failed near the end.
*/
int clean;
/*
* Result of merge. If !clean, represents what would go in worktree
* (thus possibly including files containing conflict markers).
*/
struct tree *tree;
/*
* Additional metadata used by merge_switch_to_result() or future calls
* to merge_incore_*(). Includes data needed to update the index (if
* !clean) and to print "CONFLICT" messages. Not for external use.
*/
void *priv;
/* Also private */
unsigned _properly_initialized;
};
/*
* rename-detecting three-way merge with recursive ancestor consolidation.
* working tree and index are untouched.
*
* merge_bases will be consumed (emptied) so make a copy if you need it.
*
* NOTE: empirically, the recursive algorithm will perform better if you
* pass the merge_bases in the order of oldest commit to the
* newest[1][2].
*
* [1] https://lore.kernel.org/git/nycvar.QRO.7.76.6.1907252055500.21907@tvgsbejvaqbjf.bet/
* [2] commit 8918b0c9c2 ("merge-recur: try to merge older merge bases
* first", 2006-08-09)
*/
void merge_incore_recursive(struct merge_options *opt,
struct commit_list *merge_bases,
struct commit *side1,
struct commit *side2,
struct merge_result *result);
/*
* rename-detecting three-way merge, no recursion.
* working tree and index are untouched.
*/
void merge_incore_nonrecursive(struct merge_options *opt,
struct tree *merge_base,
struct tree *side1,
struct tree *side2,
struct merge_result *result);
/* Update the working tree and index from head to result after incore merge */
void merge_switch_to_result(struct merge_options *opt,
struct tree *head,
struct merge_result *result,
int update_worktree_and_index,
int display_update_msgs);
/* Do needed cleanup when not calling merge_switch_to_result() */
void merge_finalize(struct merge_options *opt,
struct merge_result *result);
#endif