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This patch enhances clang's ability to check compile-time determinable
string literals as format strings, and can give FixIt hints at literals
(unlike gcc). Issue https://github.com/llvm/llvm-project/issues/55805
mentiond two compile-time string cases. And this patch partially fixes
one.
constexpr const char* foo() {
return "%s %d";
}
int main() {
printf(foo(), "abc", "def");
return 0;
}
This patch enables clang check format string for this:
<source>:4:24: warning: format specifies type 'int' but the argument has type
'const char *' [-Wformat]
printf(foo(), "abc", "def");
~~~~~ ^~~~~
<source>:2:42: note: format string is defined here
constexpr const char *foo() { return "%s %d"; }
^~
%s
1 warning generated.
Signed-off-by: YingChi Long <m...@inclyc.cn>
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D130906
Files:
clang/lib/Sema/SemaChecking.cpp
clang/test/Sema/format-strings-scanf.c
clang/test/Sema/format-strings.c
clang/test/SemaCXX/format-strings.cpp
Index: clang/test/SemaCXX/format-strings.cpp
===================================================================
--- clang/test/SemaCXX/format-strings.cpp
+++ clang/test/SemaCXX/format-strings.cpp
@@ -163,3 +163,48 @@
t::func4("Hello %s"); // expected-warning {{more '%' conversions than data arguments}}
}
}
+#if __cplusplus >= 201103L
+namespace evaluated {
+
+constexpr const char *basic() {
+ return
+"%s %d"; // expected-note {{format string is defined here}}
+}
+
+constexpr const char *correct_fmt() {
+ return
+"%d %d";
+}
+
+constexpr const char *string_linebreak() {
+ return
+"%d %d"
+"%d %s"; // expected-note {{format string is defined here}}
+}
+
+/*non-constexpr*/ const char *not_literal() {
+ return
+"%d %d"
+"%d %s";
+}
+
+constexpr const char *inner_call() {
+ return "%d %s"; // expected-note {{format string is defined here}}
+}
+
+constexpr const char *wrap_constexpr() {
+ return inner_call();
+}
+
+
+void f() {
+ printf(basic(), 1, 2); // expected-warning {{format specifies type 'char *' but the argument has type 'int'}}
+ printf(correct_fmt(), 1, 2);
+ printf(string_linebreak(), 1, 2, 3, 4); // expected-warning {{format specifies type 'char *' but the argument has type 'int'}}
+ printf(not_literal(), 1, 2, 3, 4); // expected-warning {{format string is not a string literal}}
+ printf(wrap_constexpr(), 1, 2); // expected-warning {{format specifies type 'char *' but the argument has type 'int'}}
+}
+
+
+}
+#endif
Index: clang/test/Sema/format-strings.c
===================================================================
--- clang/test/Sema/format-strings.c
+++ clang/test/Sema/format-strings.c
@@ -105,7 +105,8 @@
// expected-note@-1{{treat the string as an argument to avoid this}}
printf("yes" ?: "no %d", 1); // expected-warning{{data argument not used by format string}}
printf(0 ? "yes %s" : "no %d", 1); // no-warning
- printf(0 ? "yes %d" : "no %s", 1); // expected-warning{{format specifies type 'char *'}}
+ printf(0 ? "yes %d" : "no %s", 1); // expected-warning{{format specifies type 'char *'}} \
+ // expected-note{{format string is defined here}}
printf(0 ? "yes" : "no %d", 1); // no-warning
printf(0 ? "yes %d" : "no", 1); // expected-warning{{data argument not used by format string}}
@@ -259,8 +260,7 @@
printf(s2); // no-warning
printf(s3); // expected-warning{{not a string literal}}
// expected-note@-1{{treat the string as an argument to avoid this}}
- printf(s4); // expected-warning{{not a string literal}}
- // expected-note@-1{{treat the string as an argument to avoid this}}
+ printf(s4);
printf(s5); // expected-warning{{not a string literal}}
// expected-note@-1{{treat the string as an argument to avoid this}}
}
@@ -621,7 +621,8 @@
// Make sure that the "format string is defined here" note is not emitted
// when the original string is within the argument expression.
- printf(1 ? "yes %d" : "no %d"); // expected-warning{{more '%' conversions than data arguments}}
+ printf(1 ? "yes %d" : "no %d"); // expected-warning{{more '%' conversions than data arguments}} \
+ // expected-note {{format string is defined here}}
const char kFormat17[] = "%hu"; // expected-note{{format string is defined here}}}
printf(kFormat17, (int[]){0}); // expected-warning{{format specifies type 'unsigned short' but the argument}}
Index: clang/test/Sema/format-strings-scanf.c
===================================================================
--- clang/test/Sema/format-strings-scanf.c
+++ clang/test/Sema/format-strings-scanf.c
@@ -232,9 +232,11 @@
void check_conditional_literal(char *s, int *i) {
scanf(0 ? "%s" : "%d", i); // no warning
- scanf(1 ? "%s" : "%d", i); // expected-warning{{format specifies type 'char *'}}
+ scanf(1 ? "%s" : "%d", i); // expected-warning{{format specifies type 'char *'}} \
+ // expected-note{{format string is defined here}}
scanf(0 ? "%d %d" : "%d", i); // no warning
- scanf(1 ? "%d %d" : "%d", i); // expected-warning{{more '%' conversions than data arguments}}
+ scanf(1 ? "%d %d" : "%d", i); // expected-warning{{more '%' conversions than data arguments}} \
+ // expected-note{{format string is defined here}}
scanf(0 ? "%d %d" : "%d", i, s); // expected-warning{{data argument not used}}
scanf(1 ? "%d %s" : "%d", i, s); // no warning
scanf(i ? "%d %s" : "%d", i, s); // no warning
Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -8501,6 +8501,17 @@
// dependent. Ideally if the format string cannot be null then
// it should have a 'nonnull' attribute in the function prototype.
return SLCT_UncheckedLiteral;
+ Expr::EvalResult Result;
+ if (E->EvaluateAsRValue(Result, S.Context)) {
+ if (Result.Val.isLValue()) {
+ auto *LVE = Result.Val.getLValueBase().dyn_cast<const Expr *>();
+ if (LVE && LVE->getStmtClass() == Stmt::StringLiteralClass) {
+ return checkFormatStringExpr(
+ S, LVE, Args, APK, format_idx, firstDataArg, Type, CallType,
+ /*InFunctionCall*/ false, CheckedVarArgs, UncoveredArg, Offset);
+ }
+ }
+ }
switch (E->getStmtClass()) {
case Stmt::BinaryConditionalOperatorClass:
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