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Re: "error: static assertion failed: [...]" (was: [GCC Wiki] Update of "DiagnosticsGuidelines" by MartinSebor)


On 13/07/16 14:26, Thomas Schwinge wrote:
Hi!

I had recently noticed that given:

     #ifndef __cplusplus /* C */
     _Static_assert(0, "foo");
     #else /* C++ */
     static_assert(0, "foo");
     #endif

..., for C we diagnose:

     [...]:2:1: error: static assertion failed: "foo"
      _Static_assert(0, "foo");
      ^~~~~~~~~~~~~~

..., and for C++ we diagnost:

     [...]:4:1: error: static assertion failed: foo
      static_assert(0, "foo");
      ^~~~~~~~~~~~~

("foo" quoted vs. un-quoted.)  Assuming this difference between C and C++
diagnostics is not intentional, which one should we settle on?  I thought
I'd like the un-quoted version better, but judging by Martin's recent
wiki change (see below), "foo" is a string constant, so should be quoted
in diagnostics?  If yes, OK to commit to trunk the obvious changes (plus
any testsuite updates)?


From a diagnostics point-of-view, neither version is quoted:

c/c-parser.c: error_at (assert_loc, "static assertion failed: %E", string);

cp/semantics.c: error ("static assertion failed: %s",

To be "quoted", it would need to use either %q or %<%>. Note that %qs would produce `foo' not "foo". Nevertheless, we probably want to print 'x' for character literals and not `'x'' and "string" for string literals and not `string'. Thus, the wiki should probably be amended to clarify this.

Also, there is a substantial difference between %E and %s when the string contains control characters such as \n \t \u etc. Clang uses something similar to %E.

For comparison, we use %s to print

test.c:1:9: note: #pragma message:
string
#pragma message "\nstring"
^

Cheers,
	Manuel.


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