Fix gcc 8.1.1 compiler warnings

    CC ../shared.o
../shared.c: In function ‘expand_macro’:
../shared.c:487:3: warning: ‘strncpy’ specified bound depends on the length of the source argument [-Wstringop-overflow=]
   strncpy(name, value, len);
   ^~~~~~~~~~~~~~~~~~~~~~~~~
../shared.c:484:9: note: length computed here
   len = strlen(value);
         ^~~~~~~~~~~~~
../ui-shared.c: In function ‘cgit_repobasename’:
../ui-shared.c:136:2: warning: ‘strncpy’ specified bound 1024 equals destination size [-Wstringop-truncation]
  strncpy(rvbuf, reponame, sizeof(rvbuf));
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    CC ../ui-ssdiff.o
../ui-ssdiff.c: In function ‘replace_tabs’:
../ui-ssdiff.c:142:4: warning: ‘strncat’ output truncated copying between 1 and 8 bytes from a string of length 8 [-Wstringop-truncation]
    strncat(result, spaces, 8 - (strlen(result) % 8));
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

3 files changed, 23 insertions, 15 deletions

diff --git a/shared.c b/shared.c
index f7b64cf..609bd2a 100644
--- a/shared.c
+++ b/shared.c
@@ -476,15 +476,16 @@ static int is_token_char(char c)
 static char *expand_macro(char *name, int maxlength)
 {
         char *value;
-        int len;
+        size_t len;
 
         len = 0;
         value = getenv(name);
         if (value) {
-                len = strlen(value);
+                len = strlen(value) + 1;
                 if (len > maxlength)
                         len = maxlength;
-                strncpy(name, value, len);
+                strlcpy(name, value, len);
+                --len;
         }
         return name + len;
 }
diff --git a/ui-shared.c b/ui-shared.c
index 066a470..739505a 100644
--- a/ui-shared.c
+++ b/ui-shared.c
@@ -133,20 +133,25 @@ const char *cgit_repobasename(const char *reponame)
         static char rvbuf[1024];
         int p;
         const char *rv;
-        strncpy(rvbuf, reponame, sizeof(rvbuf));
-        if (rvbuf[sizeof(rvbuf)-1])
+        size_t len;
+
+        len = strlcpy(rvbuf, reponame, sizeof(rvbuf));
+        if (len >= sizeof(rvbuf))
                 die("cgit_repobasename: truncated repository name '%s'", reponame);
-        p = strlen(rvbuf)-1;
+        p = len - 1;
         /* strip trailing slashes */
-        while (p && rvbuf[p] == '/') rvbuf[p--] = 0;
+        while (p && rvbuf[p] == '/')
+                rvbuf[p--] = '\0';
         /* strip trailing .git */
         if (p >= 3 && starts_with(&rvbuf[p-3], ".git")) {
-                p -= 3; rvbuf[p--] = 0;
+                p -= 3;
+                rvbuf[p--] = '\0';
         }
         /* strip more trailing slashes if any */
-        while ( p && rvbuf[p] == '/') rvbuf[p--] = 0;
+        while (p && rvbuf[p] == '/')
+                rvbuf[p--] = '\0';
         /* find last slash in the remaining string */
-        rv = strrchr(rvbuf,'/');
+        rv = strrchr(rvbuf, '/');
         if (rv)
                 return ++rv;
         return rvbuf;
diff --git a/ui-ssdiff.c b/ui-ssdiff.c
index 7f261ed..68c2044 100644
--- a/ui-ssdiff.c
+++ b/ui-ssdiff.c
@@ -114,11 +114,10 @@ static char *replace_tabs(char *line)
 {
         char *prev_buf = line;
         char *cur_buf;
-        int linelen = strlen(line);
+        size_t linelen = strlen(line);
         int n_tabs = 0;
         int i;
         char *result;
-        char *spaces = "        ";
 
         if (linelen == 0) {
                 result = xmalloc(1);
@@ -126,20 +125,23 @@ static char *replace_tabs(char *line)
                 return result;
         }
 
-        for (i = 0; i < linelen; i++)
+        for (i = 0; i < linelen; i++) {
                 if (line[i] == '\t')
                         n_tabs += 1;
+        }
         result = xmalloc(linelen + n_tabs * 8 + 1);
         result[0] = '\0';
 
-        while (1) {
+        for (;;) {
                 cur_buf = strchr(prev_buf, '\t');
                 if (!cur_buf) {
                         strcat(result, prev_buf);
                         break;
                 } else {
                         strncat(result, prev_buf, cur_buf - prev_buf);
-                        strncat(result, spaces, 8 - (strlen(result) % 8));
+                        linelen = strlen(result);
+                        memset(&result[linelen], ' ', 8 - (linelen % 8));
+                        result[linelen + 8 - (linelen % 8)] = '\0';
                 }
                 prev_buf = cur_buf + 1;
         }