Crash when parsing angle brackets in template with type traits (assertion failure)

[Wesley King]

In the following scenario cppcheck will fail to fix the angle brackets, causing an assertion failure later on in TemplateSimplifier#getTemplateNamePosition:

template <typename S, enable_if_t<(is_compile_string<S>::value), int>> void i(S s);

Output from cppheck:

cppcheck: ../lib/templatesimplifier.cpp:1437: int TemplateSimplifier::getTemplateNamePosition(const Token*): Assertion `tok && tok->str() == ">"' failed.
[1]    162439 abort (core dumped)  cppcheck --verbose --enable=all --inconclusive 

Here is a test case for TestSimplifyTemplate:

void template154() {
     const char code[] = "template <typename S, enable_if_t<(is_compile_string<S>::value), int>> void i(S s);";
     const char exp[] = "template < typename S , enable_if_t < ( is_compile_string < S > :: value ) , int > > void i ( S s ) ;";
   ASSERT_EQUALS(exp, tok(code));
   }

The issue can be fixed with the following workaround (although I doubt this is the correct solution):

--- c/lib/templatesimplifier.cpp
+++ w/lib/templatesimplifier.cpp
@@ -514,7 +514,7 @@ unsigned int TemplateSimplifier::templateParameters(const Token *tok)
             return 0;

         // num/type ..
-        if (!tok->isNumber() && tok->tokType() != Token::eChar && !tok->isName() && !tok->isOp())
+        if (!tok->isNumber() && tok->tokType() != Token::eChar && !tok->isName() && !tok->isOp() && level == 0)
             return 0;
         tok = tok->next();
         if (!tok)

[versat]

Thanks for the detailed report.
I have created a ticket in Trac.
I am not familiar with such code, how do you compile it? What headers are needed to get this compiled (with -fsyntax-only)? I guess <type_traits>, but that is obviously not enough.

[Wesley King]

I stumbled on this issue in a file included from spdlog (https://github.com/gabime/spdlog/blob/v1.x/include/spdlog/fmt/bundled/format.h)
line 2567.

It looks like the key to reproducing this is using these struct defs:

struct compile_string {};

template <typename S>
struct is_compile_string : std::is_base_of<compile_string, S> {};

You should be able to reproduce the problem in that code base with

cppcheck -I include --enable=all --inconclusive src/spdlog.cpp