find_program: Find programs that are executable but not readable

This fix was first made by commit 86e6349ef7 (find_program: Find
programs that are executable but not readable, 2020-04-04,
v3.18.0-rc1~372^2) but was reverted for compatibility.  Re-introduce it
with a policy for compatibility.

Fixes: #10468

Help/manual/cmake-policies.7.rst

@@ -54,6 +54,14 @@ functions.
 Policies Introduced by CMake 3.18
 =================================
 
+.. toctree::
+   :maxdepth: 1
+
+   CMP0109: find_program() requires permission to execute but not to read. </policy/CMP0109>
+
+Policies Introduced by CMake 3.18
+=================================
+
 .. toctree::
    :maxdepth: 1
 

Help/policy/CMP0109.rst

@@ -0,0 +1,22 @@
+CMP0109
+-------
+
+:command:`find_program` requires permission to execute but not to read.
+
+In CMake 3.18 and below, the :command:`find_program` command on UNIX
+would find files that are readable without requiring execute permission,
+and would not find files that are executable without read permission.
+In CMake 3.19 and above, ``find_program`` now prefers to require execute
+permission but not read permission.  This policy provides compatibility
+with projects that have not been updated to expect the new behavior.
+
+The ``OLD`` behavior for this policy is for ``find_program`` to require
+read permission but not execute permission.
+The ``NEW`` behavior for this policy is for ``find_program`` to require
+execute permission but not read permission.
+
+This policy was introduced in CMake version 3.19.  CMake version |release|
+warns when the policy is not set and uses ``OLD`` behavior.  Use the
+:command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly.
+
+.. include:: DEPRECATED.txt

Help/release/dev/find_program-exe-no-read.rst

@@ -0,0 +1,5 @@
+find_program-exe-no-read
+------------------------
+
+* The :command:`find_program` command now requires permission to execute
+  but not to read the file found.  See policy :policy:`CMP0109`.

Source/cmFindProgramCommand.cxx

@@ -4,6 +4,7 @@
 
 #include "cmMakefile.h"
 #include "cmMessageType.h"
+#include "cmPolicies.h"
 #include "cmStateTypes.h"
 #include "cmStringAlgorithms.h"
 #include "cmSystemTools.h"
@@ -19,6 +20,7 @@ struct cmFindProgramHelper
   cmFindProgramHelper(cmMakefile* makefile, cmFindBase const* base)
     : DebugSearches("find_program", base)
     , Makefile(makefile)
+    , PolicyCMP0109(makefile->GetPolicyStatus(cmPolicies::CMP0109))
   {
 #if defined(_WIN32) || defined(__CYGWIN__) || defined(__MINGW32__)
     // Consider platform-specific extensions.
@@ -48,6 +50,8 @@ struct cmFindProgramHelper
   cmFindBaseDebugState DebugSearches;
   cmMakefile* Makefile;
 
+  cmPolicies::PolicyStatus PolicyCMP0109;
+
   void AddName(std::string const& name) { this->Names.push_back(name); }
   void SetName(std::string const& name)
   {
@@ -85,7 +89,7 @@ struct cmFindProgramHelper
       this->TestNameExt = cmStrCat(name, ext);
       this->TestPath =
         cmSystemTools::CollapseFullPath(this->TestNameExt, path);
-      bool exists = cmSystemTools::FileExists(this->TestPath, true);
+      bool exists = this->FileIsExecutable(this->TestPath);
       exists ? this->DebugSearches.FoundAt(this->TestPath)
              : this->DebugSearches.FailedAt(this->TestPath);
       if (exists) {
@@ -95,6 +99,48 @@ struct cmFindProgramHelper
     }
     return false;
   }
+  bool FileIsExecutable(std::string const& file) const
+  {
+    switch (this->PolicyCMP0109) {
+      case cmPolicies::OLD:
+        return cmSystemTools::FileExists(file, true);
+      case cmPolicies::NEW:
+      case cmPolicies::REQUIRED_ALWAYS:
+      case cmPolicies::REQUIRED_IF_USED:
+        return cmSystemTools::FileIsExecutable(file);
+      default:
+        break;
+    }
+    bool const isExeOld = cmSystemTools::FileExists(file, true);
+    bool const isExeNew = cmSystemTools::FileIsExecutable(file);
+    if (isExeNew == isExeOld) {
+      return isExeNew;
+    }
+    if (isExeNew) {
+      this->Makefile->IssueMessage(
+        MessageType::AUTHOR_WARNING,
+        cmStrCat(cmPolicies::GetPolicyWarning(cmPolicies::CMP0109),
+                 "\n"
+                 "The file\n"
+                 "  ",
+                 file,
+                 "\n"
+                 "is executable but not readable.  "
+                 "CMake is ignoring it for compatibility."));
+    } else {
+      this->Makefile->IssueMessage(
+        MessageType::AUTHOR_WARNING,
+        cmStrCat(cmPolicies::GetPolicyWarning(cmPolicies::CMP0109),
+                 "\n"
+                 "The file\n"
+                 "  ",
+                 file,
+                 "\n"
+                 "is readable but not executable.  "
+                 "CMake is using it for compatibility."));
+    }
+    return isExeOld;
+  }
 };
 
 cmFindProgramCommand::cmFindProgramCommand(cmExecutionStatus& status)

Source/cmPolicies.h

@@ -320,7 +320,10 @@ class cmMakefile;
   SELECT(POLICY, CMP0107, "An ALIAS target cannot overwrite another target.", \
          3, 18, 0, cmPolicies::WARN)                                          \
   SELECT(POLICY, CMP0108, "A target cannot link to itself through an alias.", \
-         3, 18, 0, cmPolicies::WARN)
+         3, 18, 0, cmPolicies::WARN)                                          \
+  SELECT(POLICY, CMP0109,                                                     \
+         "find_program() requires permission to execute but not to read.", 3, \
+         19, 0, cmPolicies::WARN)
 
 #define CM_SELECT_ID(F, A1, A2, A3, A4, A5, A6) F(A1)
 #define CM_FOR_EACH_POLICY_ID(POLICY)                                         \

Tests/RunCMake/find_program/CMP0109-Common.cmake

@@ -1,4 +1,7 @@
 file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/ExeNoRead" "#!/bin/sh\n")
+file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/ReadNoExe" "#ReadNoExe")
 execute_process(COMMAND chmod -r+x "${CMAKE_CURRENT_BINARY_DIR}/ExeNoRead")
 find_program(ExeNoRead_EXECUTABLE NAMES ExeNoRead NO_DEFAULT_PATH PATHS "${CMAKE_CURRENT_BINARY_DIR}")
 message(STATUS "ExeNoRead_EXECUTABLE='${ExeNoRead_EXECUTABLE}'")
+find_program(ReadNoExe_EXECUTABLE NAMES ReadNoExe NO_DEFAULT_PATH PATHS "${CMAKE_CURRENT_BINARY_DIR}")
+message(STATUS "ReadNoExe_EXECUTABLE='${ReadNoExe_EXECUTABLE}'")

Tests/RunCMake/find_program/CMP0109-NEW-stdout.txt

@@ -0,0 +1,2 @@
+-- ExeNoRead_EXECUTABLE='.*/Tests/RunCMake/find_program/CMP0109-NEW-build/ExeNoRead'
+-- ReadNoExe_EXECUTABLE='ReadNoExe_EXECUTABLE-NOTFOUND'

Tests/RunCMake/find_program/CMP0109-NEW.cmake

@@ -0,0 +1,2 @@
+cmake_policy(SET CMP0109 NEW)
+include(CMP0109-Common.cmake)

Tests/RunCMake/find_program/CMP0109-OLD-stdout.txt

@@ -0,0 +1,2 @@
+-- ExeNoRead_EXECUTABLE='ExeNoRead_EXECUTABLE-NOTFOUND'
+-- ReadNoExe_EXECUTABLE='.*/Tests/RunCMake/find_program/CMP0109-OLD-build/ReadNoExe'

Tests/RunCMake/find_program/CMP0109-OLD.cmake

@@ -0,0 +1,2 @@
+cmake_policy(SET CMP0109 OLD)
+include(CMP0109-Common.cmake)

Tests/RunCMake/find_program/CMP0109-WARN-stderr.txt

@@ -0,0 +1,29 @@
+^CMake Warning \(dev\) at CMP0109-Common.cmake:4 \(find_program\):
+  Policy CMP0109 is not set: find_program\(\) requires permission to execute
+  but not to read.  Run "cmake --help-policy CMP0109" for policy details.
+  Use the cmake_policy command to set the policy and suppress this warning.
+
+  The file
+
+    .*/Tests/RunCMake/find_program/CMP0109-WARN-build/ExeNoRead
+
+  is executable but not readable.  CMake is ignoring it for compatibility.
+Call Stack \(most recent call first\):
+  CMP0109-WARN.cmake:1 \(include\)
+  CMakeLists.txt:3 \(include\)
+This warning is for project developers.  Use -Wno-dev to suppress it.
++
+CMake Warning \(dev\) at CMP0109-Common.cmake:6 \(find_program\):
+  Policy CMP0109 is not set: find_program\(\) requires permission to execute
+  but not to read.  Run "cmake --help-policy CMP0109" for policy details.
+  Use the cmake_policy command to set the policy and suppress this warning.
+
+  The file
+
+    .*/Tests/RunCMake/find_program/CMP0109-WARN-build/ReadNoExe
+
+  is readable but not executable.  CMake is using it for compatibility.
+Call Stack \(most recent call first\):
+  CMP0109-WARN.cmake:1 \(include\)
+  CMakeLists.txt:3 \(include\)
+This warning is for project developers.  Use -Wno-dev to suppress it.$

Tests/RunCMake/find_program/CMP0109-WARN-stdout.txt

@@ -0,0 +1,2 @@
+-- ExeNoRead_EXECUTABLE='ExeNoRead_EXECUTABLE-NOTFOUND'
+-- ReadNoExe_EXECUTABLE='.*/Tests/RunCMake/find_program/CMP0109-WARN-build/ReadNoExe'

Tests/RunCMake/find_program/CMP0109-WARN.cmake

@@ -0,0 +1 @@
+include(CMP0109-Common.cmake)

Tests/RunCMake/find_program/ExeNoRead-stdout.txt

@@ -1 +0,0 @@
--- ExeNoRead_EXECUTABLE='ExeNoRead_EXECUTABLE-NOTFOUND'

Tests/RunCMake/find_program/RunCMakeTest.cmake

@@ -17,7 +17,9 @@ else()
     OUTPUT_STRIP_TRAILING_WHITESPACE)
 
   if(NOT "${uid}" STREQUAL "0")
-    run_cmake(ExeNoRead)
+    run_cmake(CMP0109-WARN)
+    run_cmake(CMP0109-OLD)
+    run_cmake(CMP0109-NEW)
   endif()
 endif()