cmListFileLexer: bail out on seek-errors

If we are given a FIFO, for example, we cannot seek back after trying to
read a Byte-Order-Mark.

Closes: #16607

Source/cmListFileCache.cxx

@@ -80,6 +80,13 @@ bool cmListFileParser::ParseFile()
     return false;
   }
 
+  if (bom == cmListFileLexer_BOM_Broken) {
+    cmListFileLexer_SetFileName(this->Lexer, CM_NULLPTR, CM_NULLPTR);
+    this->IssueFileOpenError("Error while reading Byte-Order-Mark. "
+                             "File not seekable?");
+    return false;
+  }
+
   // Verify the Byte-Order-Mark, if any.
   if (bom != cmListFileLexer_BOM_None && bom != cmListFileLexer_BOM_UTF8) {
     cmListFileLexer_SetFileName(this->Lexer, CM_NULLPTR, CM_NULLPTR);

Source/cmListFileLexer.c

@@ -2559,11 +2559,15 @@ static cmListFileLexer_BOM cmListFileLexer_ReadBOM(FILE* f)
       if (fread(b, 1, 2, f) == 2 && b[0] == 0 && b[1] == 0) {
         return cmListFileLexer_BOM_UTF32LE;
       }
-      fsetpos(f, &p);
+      if (fsetpos(f, &p) != 0) {
+        return cmListFileLexer_BOM_Broken;
+      }
       return cmListFileLexer_BOM_UTF16LE;
     }
   }
-  rewind(f);
+  if (fseek(f, 0, SEEK_SET) != 0) {
+    return cmListFileLexer_BOM_Broken;
+  }
   return cmListFileLexer_BOM_None;
 }
 

Source/cmListFileLexer.h

@@ -32,6 +32,7 @@ struct cmListFileLexer_Token_s
 enum cmListFileLexer_BOM_e
 {
   cmListFileLexer_BOM_None,
+  cmListFileLexer_BOM_Broken,
   cmListFileLexer_BOM_UTF8,
   cmListFileLexer_BOM_UTF16BE,
   cmListFileLexer_BOM_UTF16LE,

Tests/RunCMake/CMakeLists.txt

@@ -290,7 +290,7 @@ add_RunCMake_test(target_link_libraries)
 
 add_RunCMake_test(target_compile_features)
 add_RunCMake_test(CheckModules)
-add_RunCMake_test(CommandLine)
+add_RunCMake_test(CommandLine -DCMAKE_SYSTEM_NAME=${CMAKE_SYSTEM_NAME})
 add_RunCMake_test(CommandLineTar)
 
 add_RunCMake_test(install)

Tests/RunCMake/CommandLine/RunCMakeTest.cmake

@@ -1,3 +1,5 @@
+cmake_minimum_required(VERSION 3.1)
+
 include(RunCMake)
 
 run_cmake_command(NoArgs ${CMAKE_COMMAND})
@@ -301,3 +303,14 @@ set(CMAKE_RELATIVE_PATH_TOP_BINARY \"${RunCMake_TEST_BINARY_DIR}\")
     )
 endfunction()
 run_cmake_depends()
+
+function(reject_fifo)
+  find_program(BASH_EXECUTABLE bash)
+  if(BASH_EXECUTABLE)
+    set(BASH_COMMAND_ARGUMENT "'${CMAKE_COMMAND}' -P <(echo 'return()')")
+    run_cmake_command(reject_fifo ${BASH_EXECUTABLE} -c ${BASH_COMMAND_ARGUMENT})
+  endif()
+endfunction()
+if(CMAKE_HOST_UNIX AND NOT CMAKE_SYSTEM_NAME STREQUAL "CYGWIN")
+  reject_fifo()
+endif()

Tests/RunCMake/CommandLine/reject_fifo-result.txt

@@ -0,0 +1 @@
+1

Tests/RunCMake/CommandLine/reject_fifo-stderr.txt

@@ -0,0 +1,2 @@
+CMake Error in .*
+  Error while reading Byte-Order-Mark\.  File not seekable\?