Warn about non-standard format strings (pr12017)

This adds the -Wformat-non-standard flag (off by default,
enabled by -pedantic), which warns about non-standard
things in format strings (such as the 'q' length modifier,
the 'S' conversion specifier, etc.)

llvm-svn: 151154

3 files changed, 35 insertions, 7 deletions

diff --git a/clang/test/Sema/format-strings-c90.c b/clang/test/Sema/format-strings-c90.c
index 0b32e82d872..63d58532cb8 100644
--- a/clang/test/Sema/format-strings-c90.c
+++ b/clang/test/Sema/format-strings-c90.c
@@ -5,9 +5,8 @@ int scanf(const char * restrict, ...);
 int printf(const char *restrict, ...);
 
 void foo(char **sp, float *fp, int *ip) {
-  /* TODO: Warn that the 'a' length modifier is an extension. */
-  scanf("%as", sp);
-  scanf("%a[abc]", sp);
+  scanf("%as", sp); /* expected-warning{{'a' is a non-standard length modifier}} */
+  scanf("%a[abc]", sp); /* expected-warning{{'a' is a non-standard length modifier}} */
 
   /* TODO: Warn that the 'a' conversion specifier is a C99 feature. */
   scanf("%a", fp);
@@ -21,7 +20,11 @@ void foo(char **sp, float *fp, int *ip) {
   scanf("%da", ip);
 
   /* Test argument type check for the 'a' length modifier. */
-  scanf("%as", fp); /* expected-warning{{format specifies type 'char **' but the argument has type 'float *'}} */
-  scanf("%aS", fp); /* expected-warning{{format specifies type 'wchar_t **' (aka 'int **') but the argument has type 'float *'}} */
-  scanf("%a[abc]", fp); /* expected-warning{{format specifies type 'char **' but the argument has type 'float *'}} */
+  scanf("%as", fp); /* expected-warning{{format specifies type 'char **' but the argument has type 'float *'}}
+                       expected-warning{{'a' is a non-standard length modifier}} */
+  scanf("%aS", fp); /* expected-warning{{format specifies type 'wchar_t **' (aka 'int **') but the argument has type 'float *'}}
+                       expected-warning{{'a' is a non-standard length modifier}}
+                       expected-warning{{'S' is a non-standard conversion specifier}} */
+  scanf("%a[abc]", fp); /* expected-warning{{format specifies type 'char **' but the argument has type 'float *'}}
+                           expected-warning{{'a' is a non-standard length modifier}} */
 }
diff --git a/clang/test/Sema/format-strings-non-standard.c b/clang/test/Sema/format-strings-non-standard.c
new file mode 100644
index 00000000000..a24d43a6e1d
--- /dev/null
+++ b/clang/test/Sema/format-strings-non-standard.c
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c99 -pedantic %s
+
+int printf(const char *restrict, ...);
+int scanf(const char * restrict, ...);
+
+void f(void) {
+  char *cp;
+
+  // The 'q' length modifier.
+  printf("%qd", (long long)42); // expected-warning{{'q' is a non-standard length modifier}}
+  scanf("%qd", (long long *)0); // expected-warning{{'q' is a non-standard length modifier}}
+
+  // The 'm' length modifier.
+  scanf("%ms", &cp); // expected-warning{{'m' is a non-standard length modifier}}
+
+  // The 'S' and 'C' conversion specifiers.
+  printf("%S", L"foo"); // expected-warning{{'S' is a non-standard conversion specifier}}
+  printf("%C", L'x'); // expected-warning{{'C' is a non-standard conversion specifier}}
+
+  // Combining 'L' with an integer conversion specifier.
+  printf("%Li", (long long)42); // expected-warning{{using the length modifier 'L' with the conversion specifier 'i' is non-standard}}
+  printf("%Lo", (long long)42); // expected-warning{{using the length modifier 'L' with the conversion specifier 'o' is non-standard}}
+  printf("%Lu", (long long)42); // expected-warning{{using the length modifier 'L' with the conversion specifier 'u' is non-standard}}
+  printf("%Lx", (long long)42); // expected-warning{{using the length modifier 'L' with the conversion specifier 'x' is non-standard}}
+  printf("%LX", (long long)42); // expected-warning{{using the length modifier 'L' with the conversion specifier 'X' is non-standard}}
+}
diff --git a/clang/test/Sema/format-strings.c b/clang/test/Sema/format-strings.c
index 55b8201fd39..086c5c6d6fe 100644
--- a/clang/test/Sema/format-strings.c
+++ b/clang/test/Sema/format-strings.c
@@ -268,7 +268,6 @@ void test_unicode_conversions(wchar_t *s) {
   // FIXME: This test reports inconsistent results. On Windows, '%C' expects
   // 'unsigned short'.
   // printf("%C", 10);
-  // FIXME: we report the expected type as 'int*' instead of 'wchar_t*'
   printf("%S", "hello"); // expected-warning{{but the argument has type 'char *'}}
 }