[object] Fix reproducer crash when input file has no contents

lib/Input/Input.cpp

@@ -69,6 +69,8 @@ bool Input::resolvePathMappingFile(const LinkerConfig &PConfig) {
       Input::getMemoryAreaForPath(FileName, PConfig.getDiagEngine());
   if (!InputMem)
     InputMem = createMemoryArea(FileName, PConfig.getDiagEngine());
+  if (!InputMem)
+    return false; // File does not exist;
   setMemArea(InputMem);
   // All queries to return the name of the Input return FileName for the main
   // driver.

test/Common/standalone/EmptyInputFile/EmptyInputFile.test

@@ -0,0 +1,17 @@
+#---EmptyInputFile.test----------- Executable -----------------#
+#BEGIN_COMMENT
+# Verify that ELD handles empty input files gracefully for:
+# 1. Direct empty object file
+# 2. Archive containing empty member
+# 3. Thin archive containing empty member
+#END_COMMENT
+#START_TEST
+RUN: %clang %clangopts -o %t1.o %p/Inputs/1.c -c
+RUN: %touch %t1.empty.o
+RUN: %ar rcs %t1.a %t1.o %t1.empty.o
+RUN: %ar rcsT %t1.thin.a %t1.o %t1.empty.o
+RUN: %link %emulation %linkopts %t1.empty.o 2>&1 | %filecheck %s --check-prefix=EMPTY --allow-empty
+RUN: %link %emulation %linkopts %t1.a 2>&1
+RUN: %link %emulation %linkopts %t1.thin.a 2>&1
+#END_TEST
+EMPTY: Input file {{.*}} has no contents

test/Common/standalone/EmptyInputFile/Inputs/1.c

@@ -0,0 +1 @@
+int main() { return 0; }

test/Common/standalone/EmptyInputFile/Inputs/script.t

@@ -0,0 +1 @@
+GROUP(empty.o)

test/Common/standalone/MissingMappingFileInput/Inputs/main.c

@@ -0,0 +1 @@
+int main() { return 0; }

test/Common/standalone/MissingMappingFileInput/Inputs/mapping_missing.ini

@@ -0,0 +1,2 @@
+[Hash]
+missing.t=DOESNOTEXIST

test/Common/standalone/MissingMappingFileInput/Inputs/missing.t

@@ -0,0 +1 @@
+GROUP(/lib64/libmissing.so)

test/Common/standalone/MissingMappingFileInput/MissingMappingFileInput.test

@@ -0,0 +1,14 @@
+#---MissingMappingFileInput.test----------- Executable -----------------#
+#BEGIN_COMMENT
+# Verify that ELD handles gracefully when --mapping-file maps an input
+# to a file that does not exist on disk.
+# ELD should report a fatal error instead of crashing with a segfault.
+#END_COMMENT
+#START_TEST
+RUN: %clang %clangopts -c %p/Inputs/main.c -o %t1.o
+RUN: %not %link %linkopts %t1.o \
+RUN:   -T %p/Inputs/missing.t \
+RUN:   --mapping-file=%p/Inputs/mapping_missing.ini \
+RUN:   2>&1 | %filecheck %s
+#END_TEST
+CHECK: cannot read file