compiler: avoid undefined behavior in Import::read
For some implementations of Stream, advancing the stream will invalidate
the previously-returned peek buffer. Copy the peek buffer before
advancing in Import::read to avoid this undefined behavior.
Change-Id: Icfd56cf5e6f0d94a582d44e63bc51e75c24b8804
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/259438
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Than McIntosh <thanm@google.com>
diff --git a/go/gogo.cc b/go/gogo.cc
index aef1c47..f40f131 100644
--- a/go/gogo.cc
+++ b/go/gogo.cc
@@ -6212,7 +6212,7 @@
return false;
}
- *body = imp->read(static_cast<size_t>(llen));
+ imp->read(static_cast<size_t>(llen), body);
}
return true;
diff --git a/go/import.cc b/go/import.cc
index 081afef..c6c1178 100644
--- a/go/import.cc
+++ b/go/import.cc
@@ -1375,8 +1375,8 @@
// Read LENGTH bytes from the stream.
-std::string
-Import::read(size_t length)
+void
+Import::read(size_t length, std::string* out)
{
const char* data;
if (!this->stream_->peek(length, &data))
@@ -1385,10 +1385,11 @@
go_error_at(this->location_, "import error at %d: expected %d bytes",
this->stream_->pos(), static_cast<int>(length));
this->stream_->set_saw_error();
- return "";
+ *out = std::string("");
+ return;
}
+ *out = std::string(data, length);
this->advance(length);
- return std::string(data, length);
}
// Turn a string into a integer with appropriate error handling.
diff --git a/go/import.h b/go/import.h
index b12b3b8..1d8aae4 100644
--- a/go/import.h
+++ b/go/import.h
@@ -240,10 +240,10 @@
get_char()
{ return this->stream_->get_char(); }
- // Read LENGTH characters into a string and advance past them. On
- // EOF reports an error and returns an empty string.
- std::string
- read(size_t length);
+ // Read LENGTH characters into *OUT and advance past them. On
+ // EOF reports an error and sets *OUT to an empty string.
+ void
+ read(size_t length, std::string* out);
// Return true at the end of the stream.
bool
