Lengthen string comparisons to unblock arm_aarch64 code path

Effectively checks that the strings being compared start and end with
the specified characters (by including the terminating NUL byte of the
fixed string), rather than only checking that a string *starts with*
the non-null ASCII characters of the fixed string in the comparison.

For example, comparing the first three characters of "pen" and "pencil"
would be a match ("pen" == "pen"). Comparing the first four bytes
instead, we get "pen[NUL byte]" != "penc".

Prevents ambiguity between "arm" and "arm_aarch64", which makes the
"arm_aarch64" code path reachable again in the large if/else of
string comparisons.

Author: DeeDeeG

src/appimagetool.c

@@ -351,29 +351,29 @@ void extract_arch_from_text(gchar *archname, const gchar* sourcename, bool* arch
         if (archname) {
             replacestr(archname, "-", "_");
             replacestr(archname, " ", "_");
-            if (g_ascii_strncasecmp("i386", archname, 4) == 0
-                    || g_ascii_strncasecmp("i486", archname, 4) == 0
-                    || g_ascii_strncasecmp("i586", archname, 4) == 0
-                    || g_ascii_strncasecmp("i686", archname, 4) == 0
-                    || g_ascii_strncasecmp("intel_80386", archname, 11) == 0
-                    || g_ascii_strncasecmp("intel_80486", archname, 11) == 0
-                    || g_ascii_strncasecmp("intel_80586", archname, 11) == 0
-                    || g_ascii_strncasecmp("intel_80686", archname, 11) == 0
+            if (g_ascii_strncasecmp("i386", archname, 5) == 0
+                    || g_ascii_strncasecmp("i486", archname, 5) == 0
+                    || g_ascii_strncasecmp("i586", archname, 5) == 0
+                    || g_ascii_strncasecmp("i686", archname, 5) == 0
+                    || g_ascii_strncasecmp("intel_80386", archname, 12) == 0
+                    || g_ascii_strncasecmp("intel_80486", archname, 12) == 0
+                    || g_ascii_strncasecmp("intel_80586", archname, 12) == 0
+                    || g_ascii_strncasecmp("intel_80686", archname, 12) == 0
                     ) {
                 archs[fARCH_i686] = 1;
                 if (verbose)
                     fprintf(stderr, "%s used for determining architecture i386\n", sourcename);
-            } else if (g_ascii_strncasecmp("x86_64", archname, 6) == 0) {
+            } else if (g_ascii_strncasecmp("x86_64", archname, 7) == 0) {
                 archs[fARCH_x86_64] = 1;
                 if (verbose)
                     fprintf(stderr, "%s used for determining architecture x86_64\n", sourcename);
-            } else if (g_ascii_strncasecmp("arm", archname, 3) == 0 ||
-                       g_ascii_strncasecmp("armhf", archname, 5) == 0) {
+            } else if (g_ascii_strncasecmp("arm", archname, 4) == 0 ||
+                       g_ascii_strncasecmp("armhf", archname, 6) == 0) {
                 archs[fARCH_armhf] = 1;
                 if (verbose)
                     fprintf(stderr, "%s used for determining architecture ARM\n", sourcename);
-            } else if (g_ascii_strncasecmp("arm_aarch64", archname, 11) == 0 ||
-                       g_ascii_strncasecmp("aarch64", archname, 7) == 0) {
+            } else if (g_ascii_strncasecmp("arm_aarch64", archname, 12) == 0 ||
+                       g_ascii_strncasecmp("aarch64", archname, 8) == 0) {
                 archs[fARCH_aarch64] = 1;
                 if (verbose)
                     fprintf(stderr, "%s used for determining architecture ARM aarch64\n", sourcename);