Modified format-string checking to not emit a warning when all of the
following hold:
(1) A vprintf-like function is called that takes the argument list via a
via_list argument.
(2) The format string is a non-literal that is the parameter value of
the enclosing function, e.g:
void logmessage(const char *fmt,...) {
va_list ap;
va_start(ap,fmt);
fprintf(fmt,ap); // Do not emit a warning.
}
In the future this special case will be enhanced to consult the "format"
attribute attached to a function declaration instead of just allowing a blank
check for all function parameters to be used as format strings to vprintf-like
functions. This will happen when more support for attributes becomes
available.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@45114 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Sema/SemaChecking.cpp b/Sema/SemaChecking.cpp
index 38b93ab..b366a2b 100644
--- a/Sema/SemaChecking.cpp
+++ b/Sema/SemaChecking.cpp
@@ -237,8 +237,32 @@
StringLiteral *FExpr = dyn_cast<StringLiteral>(OrigFormatExpr);
if (FExpr == NULL) {
- Diag(Args[format_idx]->getLocStart(),
- diag::warn_printf_not_string_constant, Fn->getSourceRange());
+ // For vprintf* functions (i.e., HasVAListArg==true), we add a
+ // special check to see if the format string is a function parameter
+ // of the function calling the printf function. If the function
+ // has an attribute indicating it is a printf-like function, then we
+ // should suppress warnings concerning non-literals being used in a call
+ // to a vprintf function. For example:
+ //
+ // void
+ // logmessage(char const *fmt __attribute__ (format (printf, 1, 2)), ...) {
+ // va_list ap;
+ // va_start(ap, fmt);
+ // vprintf(fmt, ap); // Do NOT emit a warning about "fmt".
+ // ...
+ //
+ //
+ // FIXME: We don't have full attribute support yet, so just check to see
+ // if the argument is a DeclRefExpr that references a parameter. We'll
+ // add proper support for checking the attribute later.
+ if (HasVAListArg)
+ if (DeclRefExpr* DR = dyn_cast<DeclRefExpr>(IgnoreParen(OrigFormatExpr)))
+ if (isa<ParmVarDecl>(DR->getDecl()))
+ return;
+
+ Diag(Args[format_idx]->getLocStart(), diag::warn_printf_not_string_constant,
+ Fn->getSourceRange());
+
return;
}