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diff: avoid applying offsets to null pointer

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This was the only instance of undefined behavior I could find so far.
This commit is contained in:
Piotr Pawel Stefaniak 2021-09-05 18:59:08 +02:00
parent bcf2e78dc4
commit 2171b2cbe0
1 changed files with 6 additions and 3 deletions
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9
usr.bin/diff/diffreg.c
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@ -255,7 +255,6 @@ diffreg(char *file1, char *file2, int flags, int capsicum)
anychange = 0;
lastline = 0;
lastmatchline = 0;
context_vec_ptr = context_vec_start - 1;
/*
* hw excludes padding and make sure when -t is not used,
@ -1050,8 +1049,12 @@ change(char *file1, FILE *f1, char *file2, FILE *f2, int a, int b, int c, int d,
/*
* Allocate change records as needed.
*/
if (context_vec_ptr == context_vec_end - 1) {
ptrdiff_t offset = context_vec_ptr - context_vec_start;
if (context_vec_start == NULL ||
context_vec_ptr == context_vec_end - 1) {
ptrdiff_t offset = -1;
if (context_vec_start != NULL)
offset = context_vec_ptr - context_vec_start;
max_context <<= 1;
context_vec_start = xreallocarray(context_vec_start,
max_context, sizeof(*context_vec_start));