Hello, gameoftrees@,

I noticed a bug in got, where typing `got -c <root commit> file' causes
a segfault. The issue is caused by the NULL pointer tree being accessed
in find_entry_by_name() in lib/object.c. I fixed the problem the obvious
way by immediately returning NULL if tree is NULL. Now, however, it
instead outputs error messages like this:

got: file: no such entry found in tree

Is this OK, or should there be a more informative message? Either way, I
don't think am familiar with the sources enough yet to make the fix much
better.

See the backtrace and the diff below.

Alexander

$ ~/bin/got diff -c 4027f31 Makefile
Segmentation fault (core dumped)
$ gdb ~/bin/got got.core
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This GDB was configured as "amd64-unknown-openbsd7.3"...
Core was generated by `got'.
Program terminated with signal 11, Segmentation fault.
Loaded symbols for /home/aa/bin/got
Reading symbols from /usr/lib/libutil.so.16.0...done.
Loaded symbols for /usr/lib/libutil.so.16.0
Reading symbols from /usr/lib/libz.so.7.0...done.
Loaded symbols for /usr/lib/libz.so.7.0
Reading symbols from /usr/lib/libm.so.10.1...done.
Loaded symbols for /usr/lib/libm.so.10.1
Reading symbols from /usr/lib/libc.so.97.0...done.
Loaded symbols for /usr/lib/libc.so.97.0
Reading symbols from /usr/libexec/ld.so...Error while reading shared library symbols:
Dwarf Error: wrong version in compilation unit header (is 4, should be 2) [in module /usr/libexec/ld.so]
#0  find_entry_by_name (tree=0x0, name=0x148d5615f80 "Makefile", len=8)
    at /home/aa/ar/got/got/../lib/object.c:541
541             for (i = 0; i < tree->nentries; i++) {
(gdb) bt
#0  find_entry_by_name (tree=0x0, name=0x148d5615f80 "Makefile", len=8)
    at /home/aa/ar/got/got/../lib/object.c:541
#1  0x00000146aa825fae in got_object_tree_find_path (id=0x7b67ea463c10, mode=0x7b67ea463bdc,
    repo=0x1499d7a9460, tree=0x0, path=0x148d5615f80 "Makefile")
    at /home/aa/ar/got/got/../lib/object.c:589
#2  0x00000146aa81d4d5 in diff_paths (tree1=0x0, tree2=0x148d561f6a0, f1=0x14930cfb3d0,
    f2=0x14930cfb468, fd1=67, fd2=75, paths=0x7b67ea464158, repo=0x1499d7a9460,
    cb=0x146aa819160 <got_diff_blob_output_unidiff>, cb_arg=0x7b67ea463cc8)
    at /home/aa/ar/got/got/../lib/diff.c:1102
#3  0x00000146aa81bdff in diff_objects_as_trees (lines=0x0, nlines=0x0, f1=0x14930cfb3d0,
    f2=0x14930cfb468, fd1=67, fd2=75, id1=0x0, id2=0x148d561fe20, paths=0x7b67ea464158,
    label1=0x146aa7dbe8a "", label2=0x146aa7dbe8a "", diff_context=3, ignore_whitespace=0,
    force_text_diff=0, dsa=0x0, repo=0x1499d7a9460, outfile=0x14930cfb500,
    diff_algo=GOT_DIFF_ALGORITHM_PATIENCE) at /home/aa/ar/got/got/../lib/diff.c:1270
#4  0x00000146aa81c195 in got_diff_objects_as_commits (lines=0x0, nlines=0x0, f1=0x14930cfb3d0,
    f2=0x14930cfb468, fd1=67, fd2=75, id1=0x0, id2=0x148d55ff2a0, paths=0x7b67ea464158,
    diff_algo=GOT_DIFF_ALGORITHM_PATIENCE, diff_context=3, ignore_whitespace=0, force_text_diff=0,
    dsa=0x0, repo=0x1499d7a9460, outfile=0x14930cfb500) at /home/aa/ar/got/got/../lib/diff.c:1385
#5  0x00000146aa7f4a11 in cmd_diff (argc=1, argv=0x7b67ea464348) at /home/aa/ar/got/got/got.c:5483
#6  0x00000146aa7ed9f7 in main (argc=4, argv=0x7b67ea464330) at /home/aa/ar/got/got/got.c:261
Current language:  auto; currently minimal
(gdb)


diff /home/aa/ar/got
commit - 1f8d584437c06db990ac352cce06402c80b1f6a4
path + /home/aa/ar/got
blob - 2e12a69bb09622ca93b1e6240e2f9d4b5f204a91
file + lib/object.c
--- lib/object.c
+++ lib/object.c
@@ -537,6 +537,9 @@ find_entry_by_name(struct got_tree_object *tree, const
 {
 	int i;
 
+	if (!tree)
+		return NULL;
+
 	/* Note that tree entries are sorted in strncmp() order. */
 	for (i = 0; i < tree->nentries; i++) {
 		struct got_tree_entry *te = &tree->entries[i];