[flang-commits] [flang] f48f844 - [flang] Fix prescanner bug w/ empty macros in line continuation (#141274)

[via flang-commits]

Author: Peter Klausler
Date: 2025-05-28T14:01:55-07:00
New Revision: f48f844f3ccef16dc5bb3ac6e7be582f01d45317

URL: https://github.com/llvm/llvm-project/commit/f48f844f3ccef16dc5bb3ac6e7be582f01d45317
DIFF: https://github.com/llvm/llvm-project/commit/f48f844f3ccef16dc5bb3ac6e7be582f01d45317.diff

LOG: [flang] Fix prescanner bug w/ empty macros in line continuation (#141274)

When processing free form source line continuation, the prescanner
treats empty keyword macros as if they were spaces or tabs. After
skipping over them, however, there's code that only works if the skipped
characters ended with an actual space or tab. If the last skipped item
was an empty keyword macro's name, the last character of that name would
end up being the first character of the continuation line. Fix.

Added: 
    flang/test/Preprocessing/bug890.F90

Modified: 
    flang/lib/Parser/prescan.cpp

Removed: 
    


################################################################################
diff  --git a/flang/lib/Parser/prescan.cpp b/flang/lib/Parser/prescan.cpp
index 3bc2ea0b37508..9aef0c9981e3c 100644
--- a/flang/lib/Parser/prescan.cpp
+++ b/flang/lib/Parser/prescan.cpp
@@ -1473,7 +1473,7 @@ const char *Prescanner::FreeFormContinuationLine(bool ampersand) {
             GetProvenanceRange(p, p + 1),
             "Character literal continuation line should have been preceded by '&'"_port_en_US);
       }
-    } else if (p > lineStart) {
+    } else if (p > lineStart && IsSpaceOrTab(p - 1)) {
       --p;
     } else {
       insertASpace_ = true;

diff  --git a/flang/test/Preprocessing/bug890.F90 b/flang/test/Preprocessing/bug890.F90
new file mode 100644
index 0000000000000..0ce2d8c3f1569
--- /dev/null
+++ b/flang/test/Preprocessing/bug890.F90
@@ -0,0 +1,6 @@
+! RUN: %flang -E %s 2>&1 | FileCheck %s
+!CHECK: subroutine sub()
+#define empty
+subroutine sub ( &
+  empty)
+end