BLI: add macro to indicate unreachable code

This adds a `BLI_assert_unreachable()` macro, that should be used instead
of `BLI_assert(false)` in many places.

* `BLI_assert_unreachable` provides more information than `BLI_assert(false)`
  to people reading the code.
* `BLI_assert_unreachable` will print an error to `stderr` in a release build.
  This makes it more likely that we will get bug reports when the assumptions
  of a developer were wrong.

Differential Revision: https://developer.blender.org/D10780

1 files changed, 6 insertions, 0 deletions

diff --git a/source/blender/blenlib/intern/BLI_assert.c b/source/blender/blenlib/intern/BLI_assert.c
index f397cdcd8a9..887f583242f 100644
--- a/source/blender/blenlib/intern/BLI_assert.c
+++ b/source/blender/blenlib/intern/BLI_assert.c
@@ -31,6 +31,12 @@ void _BLI_assert_print_pos(const char *file, const int line, const char *functio
   fprintf(stderr, "BLI_assert failed: %s:%d, %s(), at \'%s\'\n", file, line, function, id);
 }
 
+void _BLI_assert_unreachable_print(const char *file, const int line, const char *function)
+{
+  fprintf(stderr, "Code marked as unreachable has been executed. Please report this as a bug.\n");
+  fprintf(stderr, "Error found at %s:%d in %s.\n", file, line, function);
+}
+
 void _BLI_assert_print_backtrace(void)
 {
 #ifndef NDEBUG