From 67e2130c963bb3d9d437f00f5d6b8e95d2f5fb18 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Fri, 20 Nov 2020 09:45:14 -0500
Subject: Makefiles: Fix CMAKE_EXPORT_COMPILE_COMMANDS crash with custom
 compile rule

Fixes: #21471
---
 Source/cmMakefileTargetGenerator.cxx                     | 16 ++++++++++------
 .../ExportCompileCommands/CustomCompileRule.cmake        |  5 +++++
 Tests/RunCMake/ExportCompileCommands/RunCMakeTest.cmake  |  1 +
 3 files changed, 16 insertions(+), 6 deletions(-)
 create mode 100644 Tests/RunCMake/ExportCompileCommands/CustomCompileRule.cmake

diff --git a/Source/cmMakefileTargetGenerator.cxx b/Source/cmMakefileTargetGenerator.cxx
index 5f97d86..6e6c8df 100644
--- a/Source/cmMakefileTargetGenerator.cxx
+++ b/Source/cmMakefileTargetGenerator.cxx
@@ -838,13 +838,17 @@ void cmMakefileTargetGenerator::WriteObjectRuleFiles(
       compileCommand.replace(compileCommand.find(langFlags), langFlags.size(),
                              this->GetFlags(lang, this->GetConfigName()));
       std::string langDefines = std::string("$(") + lang + "_DEFINES)";
-      compileCommand.replace(compileCommand.find(langDefines),
-                             langDefines.size(),
-                             this->GetDefines(lang, this->GetConfigName()));
+      std::string::size_type ldPos = compileCommand.find(langDefines);
+      if (ldPos != std::string::npos) {
+        compileCommand.replace(ldPos, langDefines.size(),
+                               this->GetDefines(lang, this->GetConfigName()));
+      }
       std::string langIncludes = std::string("$(") + lang + "_INCLUDES)";
-      compileCommand.replace(compileCommand.find(langIncludes),
-                             langIncludes.size(),
-                             this->GetIncludes(lang, this->GetConfigName()));
+      std::string::size_type liPos = compileCommand.find(langIncludes);
+      if (liPos != std::string::npos) {
+        compileCommand.replace(liPos, langIncludes.size(),
+                               this->GetIncludes(lang, this->GetConfigName()));
+      }
 
       cmProp eliminate[] = {
         this->Makefile->GetDefinition("CMAKE_START_TEMP_FILE"),
diff --git a/Tests/RunCMake/ExportCompileCommands/CustomCompileRule.cmake b/Tests/RunCMake/ExportCompileCommands/CustomCompileRule.cmake
new file mode 100644
index 0000000..12368a2
--- /dev/null
+++ b/Tests/RunCMake/ExportCompileCommands/CustomCompileRule.cmake
@@ -0,0 +1,5 @@
+enable_language(C)
+add_library(empty STATIC empty.c)
+string(REPLACE "<DEFINES>" "" CMAKE_C_COMPILE_OBJECT "${CMAKE_C_COMPILE_OBJECT}")
+string(REPLACE "<INCLUDES>" "" CMAKE_C_COMPILE_OBJECT "${CMAKE_C_COMPILE_OBJECT}")
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
diff --git a/Tests/RunCMake/ExportCompileCommands/RunCMakeTest.cmake b/Tests/RunCMake/ExportCompileCommands/RunCMakeTest.cmake
index b540a04..9e7e732 100644
--- a/Tests/RunCMake/ExportCompileCommands/RunCMakeTest.cmake
+++ b/Tests/RunCMake/ExportCompileCommands/RunCMakeTest.cmake
@@ -1,3 +1,4 @@
 include(RunCMake)
 
 run_cmake_with_options(BeforeProject -DCMAKE_PROJECT_INCLUDE_BEFORE=BeforeProjectBEFORE.cmake)
+run_cmake(CustomCompileRule)
-- 
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