compat/win32: correct for incorrect compiler warning

The 'win build' job of our CI build is failing with the following error:

compat/win32/syslog.c: In function 'syslog':
compat/win32/syslog.c:53:17: error: pointer 'pos' may be used after \
				    'realloc' [-Werror=use-after-free]
   53 |                 memmove(pos + 2, pos + 1, strlen(pos));
    CC compat/poll/poll.o
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
compat/win32/syslog.c:47:23: note: call to 'realloc' here
   47 |                 str = realloc(str, st_add(++str_len, 1));
      |                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

However, between this realloc() and the use we have a line that resets
the value of 'pos'. Thus, this error is incorrect. It is likely due to a
new version of the compiler on the CI machines.

Instead of waiting for a new compiler, create a new variable to avoid
this error.

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/compat/win32/syslog.c b/compat/win32/syslog.c
index 1f8d8934cc90dc2a5988265c555271c8afd18084..0af18d88825915dec4d3a8c3cd1cfe3e6ad36a0a 100644 (file)
--- a/compat/win32/syslog.c
+++ b/compat/win32/syslog.c
@@ -44,6 +44,7 @@ void syslog(int priority, const char *fmt, ...)
 
        while ((pos = strstr(str, "%1")) != NULL) {
                size_t offset = pos - str;
+               char *new_pos;
                char *oldstr = str;
                str = realloc(str, st_add(++str_len, 1));
                if (!str) {
@@ -51,9 +52,9 @@ void syslog(int priority, const char *fmt, ...)
                        warning_errno("realloc failed");
                        return;
                }
-               pos = str + offset;
-               memmove(pos + 2, pos + 1, strlen(pos));
-               pos[1] = ' ';
+               new_pos = str + offset;
+               memmove(new_pos + 2, new_pos + 1, strlen(new_pos));
+               new_pos[1] = ' ';
        }
 
        switch (priority) {