cmIfCommand: Issue CMP0054 warning with appropriate context. (#15802)

Commit v3.4.0-rc1~494^2~4 (cmMakefile: Add API for elseif to create
backtrace., 2015-05-29) removed the use of cmMakefileCall to push/pop
execution context in favor of a new way to create backtraces.

However, a call to cmMakefile::GetExecutionContext is still invoked to
issue a contextual CMP0054 warning through cmConditionEvaluator.  As
the elseif is not part of the call stack, this resulted in trying to
access an empty vector.

Avoid the attempt at getting execution context when evaluating elseif by
constructing a context and backtrace on behalf of the cmConditionEvaluator
in all cases.

4 files changed, 29 insertions, 0 deletions

diff --git a/Tests/RunCMake/CMP0054/CMP0054-WARN-stderr.txt b/Tests/RunCMake/CMP0054/CMP0054-WARN-stderr.txt
index 3d875ae..3cfa5d2 100644
--- a/Tests/RunCMake/CMP0054/CMP0054-WARN-stderr.txt
+++ b/Tests/RunCMake/CMP0054/CMP0054-WARN-stderr.txt
@@ -9,3 +9,15 @@ CMake Warning \(dev\) at CMP0054-WARN.cmake:3 \(if\):
 Call Stack \(most recent call first\):
   CMakeLists.txt:3 \(include\)
 This warning is for project developers.  Use -Wno-dev to suppress it.
++
+CMake Warning \(dev\) at CMP0054-WARN.cmake:5 \(elseif\):
+  Policy CMP0054 is not set: Only interpret if\(\) arguments as variables or
+  keywords when unquoted.  Run "cmake --help-policy CMP0054" for policy
+  details.  Use the cmake_policy command to set the policy and suppress this
+  warning.
+
+  Quoted variables like "FOO" will no longer be dereferenced when the policy
+  is set to NEW.  Since the policy is not set the OLD behavior will be used.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/CMP0054/CMP0054-WARN.cmake b/Tests/RunCMake/CMP0054/CMP0054-WARN.cmake
index 37855fc..a608929 100644
--- a/Tests/RunCMake/CMP0054/CMP0054-WARN.cmake
+++ b/Tests/RunCMake/CMP0054/CMP0054-WARN.cmake
@@ -2,4 +2,6 @@ set(FOO "BAR")
 
 if(NOT "FOO" STREQUAL "BAR")
   message(FATAL_ERROR "The given literals should match")
+elseif("FOO" STREQUAL "BING")
+  message(FATAL_ERROR "The given literals should not match")
 endif()
diff --git a/Tests/RunCMake/CMP0054/CMP0054-keywords-WARN-stderr.txt b/Tests/RunCMake/CMP0054/CMP0054-keywords-WARN-stderr.txt
index b1ebd49..5a8c263 100644
--- a/Tests/RunCMake/CMP0054/CMP0054-keywords-WARN-stderr.txt
+++ b/Tests/RunCMake/CMP0054/CMP0054-keywords-WARN-stderr.txt
@@ -10,3 +10,16 @@ CMake Warning \(dev\) at CMP0054-keywords-WARN.cmake:1 \(if\):
 Call Stack \(most recent call first\):
   CMakeLists.txt:3 \(include\)
 This warning is for project developers.  Use -Wno-dev to suppress it.
++
+CMake Warning \(dev\) at CMP0054-keywords-WARN.cmake:3 \(elseif\):
+  Policy CMP0054 is not set: Only interpret if\(\) arguments as variables or
+  keywords when unquoted.  Run "cmake --help-policy CMP0054" for policy
+  details.  Use the cmake_policy command to set the policy and suppress this
+  warning.
+
+  Quoted keywords like "DEFINED" will no longer be interpreted as keywords
+  when the policy is set to NEW.  Since the policy is not set the OLD
+  behavior will be used.
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)
+This warning is for project developers.  Use -Wno-dev to suppress it.
diff --git a/Tests/RunCMake/CMP0054/CMP0054-keywords-WARN.cmake b/Tests/RunCMake/CMP0054/CMP0054-keywords-WARN.cmake
index ee0a623..118ab3d 100644
--- a/Tests/RunCMake/CMP0054/CMP0054-keywords-WARN.cmake
+++ b/Tests/RunCMake/CMP0054/CMP0054-keywords-WARN.cmake
@@ -1,3 +1,5 @@
 if("NOT" 1)
   message(FATAL_ERROR "[\"NOT\" 1] evaluated true")
+elseif("DEFINED" NotDefined)
+  message(FATAL_ERROR "[\"DEFINED\" NotDefined] evaluated true")
 endif()