Add option to disable RTTI in Clang [#207]

doc/flycheck.texi

@@ -600,6 +600,10 @@ Additional preprocessor definitions for @code{c/c++-clang}.
 The language standard for @code{c/c++-clang}.
 @end defopt
 
+@defopt flycheck-clang-no-rtti
+Whether to disable RTTI in @code{c/c++-clang}.
+@end defopt
+
 @defopt flycheck-clang-warnings
 Additional warnings to enable in @code{c/c++-clang}.
 @end defopt
@@ -1144,6 +1148,11 @@ string.  If omitted, it defaults to @code{list}, so by default,
 list before substitution.  Items for which the filter returns nil are
 dropped.  @xref{Option filters}, for a list of built-in option filters.
 
+@item (option-flag @var{option} @var{variable})
+This cell is substituted with @var{option}, if the value of
+@var{variable} is non-nil.  Otherwise it is simply dropped from the
+argument list.
+
 @item (eval @var{form})
 This cell is substituted with a result of evaluating @var{form}.
 @var{form} must either return a string or a list of strings, or
@@ -2819,6 +2828,12 @@ language standard for C/C++ syntax checking}
 @item
 @ghissue{207, Add @code{flycheck-clang-definitions} to set additional
 definitions for C/C++ syntax checking}
+@item
+@ghissue{207, Add @code{flycheck-clang-no-rtti} to disable RTTI for
+C/C++ syntax checking}
+@item
+Add new option cell @code{option-flag} for boolean flags in syntax
+checker commands
 @end itemize
 
 @end itemize

flycheck.el

@@ -1295,6 +1295,9 @@ error if not."
       (`(,(or `option `option-list) ,option-name ,option-var)
        (and (stringp option-name)
             (symbolp option-var)))
+      (`(option-flag ,option-name ,option-var)
+       (and (stringp option-name)
+            (symbolp option-var)))
       (`(,(or `option `option-list) ,option-name ,option-var ,prepender-or-filter)
        (and (stringp option-name)
             (-all? #'symbolp (list option-var prepender-or-filter))))
@@ -1675,6 +1678,10 @@ STRING
      return a list `(OPTION ITEM1 OPTION ITEM2 ...)'.  Otherwise
      return nil.
 
+`(option-flag OPTION VARIABLE)'
+     Retrieve the value of VARIABLE and return OPTION, if the
+     value is non-nil.  Otherwise return nil.
+
 `(eval FORM)
      Return the result of evaluating FORM in the buffer to be
      checked.  FORM must either return a string or a list of
@@ -1732,6 +1739,9 @@ are substituted within the body of cells!"
          (error "Value %S of %S for option %S is not a list of strings"
                 value variable option-name))
        (flycheck-prepend-with-option option-name value prepend-fn)))
+    (`(option-flag ,option-name ,variable)
+     (when (symbol-value variable)
+       option-name))
     (`(eval ,form)
      (let ((result (eval form)))
        (if (or (null result)
@@ -3245,6 +3255,14 @@ pass the language standard via the `-std' option."
   :safe #'stringp
   :package-version '(flycheck . "0.15"))
 
+(flycheck-def-option-var flycheck-clang-no-rtti nil c/c++-clang
+  "Whether to disable RTTI in Clang.
+
+When non-nil, disable RTTI for syntax checks, via `-fno-rtti'."
+  :type 'boolean
+  :safe #'booleanp
+  :package-version '(flycheck . "0.15"))
+
 (flycheck-def-option-var flycheck-clang-warnings '("all" "extra") c/c++-clang
   "A list of additional warnings to enable in Clang.
 
@@ -3274,6 +3292,7 @@ See URL `http://clang.llvm.org/'."
             "-fno-diagnostics-show-option" ; Do not show the corresponding
                                         ; warning group
             (option "-std=" flycheck-clang-language-standard)
+            (option-flag "-fno-rtti" flycheck-clang-no-rtti)
             (option-list "-W" flycheck-clang-warnings s-prepend)
             (option-list "-D" flycheck-clang-definitions s-prepend)
             (option-list "-I" flycheck-clang-include-path)

test/builtin-checkers-test.el

@@ -126,6 +126,15 @@
      '(8 16 "'nullptr' is a keyword in C++11" warning)
      '(8 16 "use of undeclared identifier 'nullptr'" error))))
 
+(ert-deftest checker-c/c++-clang-error-no-rtti ()
+  :expected-result (flycheck-testsuite-fail-unless-checker 'c/c++-clang)
+  (flycheck-testsuite-with-hook c++-mode-hook
+      (setq flycheck-clang-no-rtti t)
+    ;; Clang doesn't throw errors for RTTI operators :|, so we basically just
+    ;; test that the option flag doesn't cause any issues
+    (flycheck-testsuite-should-syntax-check
+     "checkers/c_c++-clang-error-rtti.cpp" 'c++-mode nil)))
+
 (ert-deftest checker-c/c++-cppcheck-error ()
   :expected-result (flycheck-testsuite-fail-unless-checker 'c/c++-cppcheck)
   (flycheck-testsuite-should-syntax-check

test/checker-api-test.el

@@ -139,6 +139,19 @@
                    '(option-list "-I" flycheck-test-option-var nil number-to-string) 'emacs-lisp)
                   :type 'wrong-type-argument)))
 
+(ert-deftest flycheck-substitute-argument-option-flag ()
+  (let ((flycheck-test-option-var nil))
+    (should-not (flycheck-substitute-argument
+                 '(option-flag "--foo" flycheck-test-option-var) 'emacs-lisp)))
+  (let ((flycheck-test-option-var t))
+    (should (equal (flycheck-substitute-argument
+                    '(option-flag "--foo" flycheck-test-option-var) 'emacs-lisp)
+                   "--foo")))
+  (let ((flycheck-test-option-var (list "bar")))
+    (should (equal (flycheck-substitute-argument
+                    '(option-flag "--foo" flycheck-test-option-var) 'emacs-lisp)
+                   "--foo"))))
+
 (ert-deftest flycheck-substitute-argument-eval ()
   (let ((flycheck-test-option-var '("Hello " "World")))
     (should (equal (flycheck-substitute-argument '(eval flycheck-test-option-var) 'emacs-lisp)
@@ -249,6 +262,19 @@
                    '(option-list "-I" flycheck-test-option-var nil number-to-string) 'emacs-lisp)
                   :type 'wrong-type-argument)))
 
+(ert-deftest flycheck-substitute-shell-argument-option-flag ()
+  (let ((flycheck-test-option-var nil))
+    (should  (s-blank? (flycheck-substitute-shell-argument
+                        '(option-flag "--foo" flycheck-test-option-var) 'emacs-lisp))))
+  (let ((flycheck-test-option-var t))
+    (should (equal (flycheck-substitute-shell-argument
+                    '(option-flag "--foo" flycheck-test-option-var) 'emacs-lisp)
+                   "--foo")))
+  (let ((flycheck-test-option-var (list "bar")))
+    (should (equal (flycheck-substitute-shell-argument
+                    '(option-flag "--foo" flycheck-test-option-var) 'emacs-lisp)
+                   "--foo"))))
+
 (ert-deftest flycheck-substitute-shell-argument-eval ()
   (mocker-let
       ((flycheck-substitute-argument

test/resources/checkers/c_c++-clang-error-rtti.cpp

@@ -0,0 +1,14 @@
+#include <iostream>
+
+using namespace std;
+
+class Base {};
+class Derived : public Base {};
+
+int main()
+{
+    Derived *d = new Derived;
+    Base *b = dynamic_cast<Base*>(d);
+    cout << b;
+    return 0;
+}