7 files changed, 11 insertions, 8 deletions
diff --git a/fastlib/src/vespa/fastlib/io/bufferedfile.h b/fastlib/src/vespa/fastlib/io/bufferedfile.h
index ab01919d91a..78c19ef8169 100644
--- a/fastlib/src/vespa/fastlib/io/bufferedfile.h
+++ b/fastlib/src/vespa/fastlib/io/bufferedfile.h
@@ -123,7 +123,7 @@ public:
      * @param dstlen The length of the destination buffer.
      * @return The number of bytes read.
      */
-    ssize_t Read(void *dst, size_t dstlen) override;
+    [[nodiscard]] ssize_t Read(void *dst, size_t dstlen) override;
     /**
      * Write one byte to the buffered file, flushing to
      * file if necessary.
diff --git a/fastos/src/tests/filetest.cpp b/fastos/src/tests/filetest.cpp
index d95580897d0..80045269c9e 100644
--- a/fastos/src/tests/filetest.cpp
+++ b/fastos/src/tests/filetest.cpp
@@ -674,7 +674,8 @@ public:
             int64_t position = file.GetPosition();
             Progress(position == 0, "File pointer should be 0 after opening file");
 
-            file.Read(buffer, 4);
+            ssize_t has_read = file.Read(buffer, 4);
+            Progress(has_read == 4, "Must read 4 bytes");
             buffer[4] = '\0';
             position = file.GetPosition();
             Progress(position == 4, "File pointer should be 4 after reading 4 bytes");
diff --git a/fastos/src/vespa/fastos/file.h b/fastos/src/vespa/fastos/file.h
index 611e179adf0..238da364d54 100644
--- a/fastos/src/vespa/fastos/file.h
+++ b/fastos/src/vespa/fastos/file.h
@@ -324,7 +324,7 @@ public:
      * @return The number of bytes which was actually read,
      *         or -1 on error.
      */
-    virtual ssize_t Read(void *buffer, size_t length) = 0;
+    [[nodiscard]] virtual ssize_t Read(void *buffer, size_t length) = 0;
 
     /**
      * Write [len] bytes from [buffer].  This is just a wrapper for
diff --git a/fastos/src/vespa/fastos/linux_file.h b/fastos/src/vespa/fastos/linux_file.h
index 6ba5cdc8fea..f3c66d49f12 100644
--- a/fastos/src/vespa/fastos/linux_file.h
+++ b/fastos/src/vespa/fastos/linux_file.h
@@ -36,7 +36,7 @@ public:
     void *AllocateDirectIOBuffer(size_t byteSize, void *&realPtr) override;
 
 
-    ssize_t Read(void *buffer, size_t len) override;
+    [[nodiscard]] ssize_t Read(void *buffer, size_t len) override;
     [[nodiscard]] ssize_t Write2(const void *buffer, size_t len) override;
     bool Open(unsigned int openFlags, const char *filename) override;
 
diff --git a/fastos/src/vespa/fastos/unix_file.h b/fastos/src/vespa/fastos/unix_file.h
index 86e89ffde95..70a8db5036e 100644
--- a/fastos/src/vespa/fastos/unix_file.h
+++ b/fastos/src/vespa/fastos/unix_file.h
@@ -58,7 +58,7 @@ public:
     { }
 
     void ReadBuf(void *buffer, size_t length, int64_t readOffset) override;
-    ssize_t Read(void *buffer, size_t len) override;
+    [[nodiscard]] ssize_t Read(void *buffer, size_t len) override;
     [[nodiscard]] ssize_t Write2(const void *buffer, size_t len) override;
     bool Open(unsigned int openFlags, const char *filename) override;
     [[nodiscard]] bool Close() override;
diff --git a/searchlib/src/vespa/searchlib/diskindex/bitvectordictionary.cpp b/searchlib/src/vespa/searchlib/diskindex/bitvectordictionary.cpp
index 29c82936076..f6dd5a318ae 100644
--- a/searchlib/src/vespa/searchlib/diskindex/bitvectordictionary.cpp
+++ b/searchlib/src/vespa/searchlib/diskindex/bitvectordictionary.cpp
@@ -53,7 +53,8 @@ BitVectorDictionary::open(const vespalib::string &pathPrefix,
         size_t bufSize = sizeof(WordSingleKey) * numEntries;
         assert(idxFile.GetSize() >= static_cast<int64_t>(idxHeaderLen + bufSize));
         if (bufSize > 0) {
-            idxFile.Read(&_entries[0], bufSize);
+            ssize_t has_read = idxFile.Read(&_entries[0], bufSize);
+            assert(has_read == ssize_t(bufSize));
         }
     }
 
diff --git a/searchlib/src/vespa/searchlib/diskindex/wordnummapper.cpp b/searchlib/src/vespa/searchlib/diskindex/wordnummapper.cpp
index cd9cd6c34da..3c74ab5ff07 100644
--- a/searchlib/src/vespa/searchlib/diskindex/wordnummapper.cpp
+++ b/searchlib/src/vespa/searchlib/diskindex/wordnummapper.cpp
@@ -2,6 +2,7 @@
 
 #include "wordnummapper.h"
 #include <vespa/fastlib/io/bufferedfile.h>
+#include <cassert>
 
 namespace search::diskindex {
 
@@ -30,8 +31,8 @@ WordNumMapping::readMappingFile(const vespalib::string &name,
     map.resize(tempfileentries + 2);
     _oldDictSize = tempfileentries;
 
-    old2newwordfile.Read(&map[1],
-                         static_cast<size_t>(tempfilesize));
+    ssize_t has_read = old2newwordfile.Read(&map[1], static_cast<size_t>(tempfilesize));
+    assert(has_read == tempfilesize);
     map[0] = noWordNum();
     map[tempfileentries + 1] = noWordNumHigh();
 }