Validate that format strings match when both caller and callee have format_matches

Author: apple-fcloutier

clang/lib/Sema/SemaChecking.cpp

@@ -6085,8 +6085,8 @@ static StringLiteralCheckType checkFormatStringExpr(
               continue;
             if (PV->getFunctionScopeIndex() == CallerFSI.FormatIdx)
               return checkFormatStringExpr(
-                  S, nullptr, PVFormatMatches->getFormatString(), Args, APK,
-                  format_idx, firstDataArg, Type, CallType,
+                  S, ReferenceFormatString, PVFormatMatches->getFormatString(),
+                  Args, APK, format_idx, firstDataArg, Type, CallType,
                   /*InFunctionCall*/ false, CheckedVarArgs, UncoveredArg,
                   Offset, IgnoreStringsWithoutSpecifiers);
           }

clang/test/Sema/format-string-matches.c

@@ -105,3 +105,19 @@ void test_freebsd_specifiers(void) {
     cvt_freebsd_D("%b");
     cvt_freebsd_D("%s %i"); // expected-warning{{format argument is a value, but it should be an auxiliary value}}
 }
+
+__attribute__((format_matches(printf, 1, "%s"))) // expected-note{{comparing with this specifier}}
+__attribute__((format_matches(os_log, 2, "%i"))) // expected-note{{comparing with this specifier}}
+void test_recv_multiple_format_strings(const char *fmt1, const char *fmt2);
+
+__attribute__((format_matches(printf, 1, "%s")))
+__attribute__((format_matches(os_log, 2, "%i")))
+void test_multiple_format_strings(const char *fmt1, const char *fmt2) {
+    test_recv_multiple_format_strings("%s", "%i");
+    test_recv_multiple_format_strings("%s", "%s"); // expected-warning{{format specifier 's' is incompatible with 'i'}}
+    test_recv_multiple_format_strings("%i", "%i"); // expected-warning{{format specifier 'i' is incompatible with 's'}}
+
+    test_recv_multiple_format_strings(fmt1, fmt2);
+    test_recv_multiple_format_strings("%.5s", fmt2);
+    test_recv_multiple_format_strings(fmt1, "%04d");
+}