diff --git a/flang/include/flang/Evaluate/integer.h b/flang/include/flang/Evaluate/integer.h
--- a/flang/include/flang/Evaluate/integer.h
+++ b/flang/include/flang/Evaluate/integer.h
@@ -805,7 +805,9 @@
           if (Part ypart{y.LEPart(k)}) {
             BigPart xy{xpart};
             xy *= ypart;
-            for (int to{j + k}; xy != 0; ++to) {
+            // && to < (2 * parts) was added to avoid GCC < 8 build failure
+            // on -Werror=array-bounds
+            for (int to{ j + k }; xy != 0 && to < (2 * parts); ++to) {
               xy += product[to];
               product[to] = xy & partMask;
               xy >>= partBits;
diff --git a/flang/lib/Decimal/big-radix-floating-point.h b/flang/lib/Decimal/big-radix-floating-point.h
--- a/flang/lib/Decimal/big-radix-floating-point.h
+++ b/flang/lib/Decimal/big-radix-floating-point.h
@@ -179,7 +179,10 @@
       if (remove >= digits_) {
         digits_ = 0;
       } else if (remove > 0) {
-        for (int j{0}; j + remove < digits_; ++j) {
+        // (&& j + remove < maxDigits) was added to avoid GCC < 8 build failure
+        // on -Werror=array-bounds
+        for (int j{ 0 }; j + remove < digits_ && (j + remove < maxDigits);
+             ++j) {
           digit_[j] = digit_[j + remove];
         }
         digits_ -= remove;