[flang] Add snippet about trigraphs

Original-commit: flang-compiler/f18@551f2ccd06861f317bfb6fe092c2274af3fc96c1
Reviewed-on: https://github.com/flang-compiler/f18/pull/45

diff --git a/flang/documentation/preprocessing.md b/flang/documentation/preprocessing.md
index c9f9965..a3cc470 100644 (file)
--- a/flang/documentation/preprocessing.md
+++ b/flang/documentation/preprocessing.md
@@ -67,6 +67,7 @@ Judgement calls, where precedents are unclear:
   line continuation marker.
 * `#define c 1` does not allow a `c` in column 1 to be used as a label
   in fixed form, rather than as a comment line indicator.
+* IBM claims to be ISO C compliant and therefore recognizes trigraph sequences.
 
 Behavior that few compilers properly support (or none), but should:
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