compiler: avoid silent truncation for string(1 << 32)

In the conversion of a constant integer to a string type, the value of
the constant integer was being silently truncated from unsigned long
to unsigned int, producing the wrong string value.  Add an explicit
overflow check to avoid this problem.

For golang/go#42790

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/272611

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 3e94dab..c14ee7e 100644 (file)
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-78c9a657fdbc9e812d39910fb93fbae4affe4360
+8cbe18aff99dbf79bd1adb9c025418e84505ffd5
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index 6bc9348..448888b 100644 (file)
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -4024,8 +4024,16 @@ Type_conversion_expression::do_string_constant_value(std::string* val) const
          unsigned long ival;
          if (nc.to_unsigned_long(&ival) == Numeric_constant::NC_UL_VALID)
            {
+             unsigned int cval = static_cast<unsigned int>(ival);
+             if (static_cast<unsigned long>(cval) != ival)
+               {
+                 go_warning_at(this->location(), 0,
+                               "unicode code point 0x%lx out of range",
+                               ival);
+                 cval = 0xfffd; // Unicode "replacement character."
+               }
              val->clear();
-             Lex::append_char(ival, true, val, this->location());
+             Lex::append_char(cval, true, val, this->location());
              return true;
            }
        }