gofrontend: correct file reading logic in Stream_from_file

The implementation of Stream_from_file mishandled several cases:

  * It reversed the check for whether bytes were already available in
    the peek buffer.

  * It considered positive return values from lseek to be an error, when
    only a -1 return value indicates an error.

Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/259437

diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 94827406df1915bbd84d948708e7ac1a855fb477..701b2d427e32b68a531dfacee224bf8661b9cefc 100644 (file)
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-801c458a562d22260ff176c26d65639dd32c8a90
+d00febdab0535546ccbf1ef634be1f23b09c8b77
 
 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/import.cc b/gcc/go/gofrontend/import.cc
index c63ae24f533d71aa745345b0980554029394f9e8..081afefa0838d6498db9f900d43724c0af5bc68f 100644 (file)
--- a/gcc/go/gofrontend/import.cc
+++ b/gcc/go/gofrontend/import.cc
@@ -1487,7 +1487,7 @@ Stream_from_file::~Stream_from_file()
 bool
 Stream_from_file::do_peek(size_t length, const char** bytes)
 {
-  if (this->data_.length() <= length)
+  if (this->data_.length() >= length)
     {
       *bytes = this->data_.data();
       return true;
@@ -1504,7 +1504,7 @@ Stream_from_file::do_peek(size_t length, const char** bytes)
       return false;
     }
 
-  if (lseek(this->fd_, - got, SEEK_CUR) != 0)
+  if (lseek(this->fd_, - got, SEEK_CUR) < 0)
     {
       if (!this->saw_error())
        go_fatal_error(Linemap::unknown_location(), "lseek failed: %m");
@@ -1524,7 +1524,7 @@ Stream_from_file::do_peek(size_t length, const char** bytes)
 void
 Stream_from_file::do_advance(size_t skip)
 {
-  if (lseek(this->fd_, skip, SEEK_CUR) != 0)
+  if (lseek(this->fd_, skip, SEEK_CUR) < 0)
     {
       if (!this->saw_error())
        go_fatal_error(Linemap::unknown_location(), "lseek failed: %m");
@@ -1532,7 +1532,7 @@ Stream_from_file::do_advance(size_t skip)
     }
   if (!this->data_.empty())
     {
-      if (this->data_.length() < skip)
+      if (this->data_.length() > skip)
        this->data_.erase(0, skip);
       else
        this->data_.clear();