maint: tighten curly brace syntax checking

Now that hanging brace offenders have been fixed, we can automate
the check, and document our style.  Done as a separate commit from
code changes, to make it easier to just backport code changes, if
that is ever needed.

* cfg.mk (sc_curly_braces_style): Catch hanging braces.
* docs/hacking.html.in: Document it.
* HACKING: Regenerate.

Signed-off-by: Eric Blake <eblake@redhat.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/HACKING b/HACKING
index 88a42864b8..add0841cb8 100644
--- a/HACKING
+++ b/HACKING
@@ -461,6 +461,33 @@ But if negating a complex condition is too ugly, then at least add braces:
       x = y;
   }
 
+Use hanging braces for compound statements: the opening brace of a compound
+statement should be on the same line as the condition being tested. Only
+top-level function bodies, nested scopes, and compound structure declarations
+should ever have { on a line by itself.
+
+  void
+  foo(int a, int b)
+  {                          // correct - function body
+      int 2d[][] = {
+        {                    // correct - complex initialization
+          1, 2,
+        },
+      };
+      if (a)
+      {                      // BAD: compound brace on its own line
+          do_stuff();
+      }
+      {                      // correct - nested scope
+          int tmp;
+          if (a < b) {       // correct - hanging brace
+              tmp = b;
+              b = a;
+              a = tmp;
+          }
+      }
+  }
+
 
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