Add a warning for empty segments

This commit improves linker diagnostics by adding a warning
diagnostic for empty segments.

Closes #116

Signed-off-by: Parth Arora <[email protected]>

Author: parth-07

include/eld/Diagnostics/DiagLayouts.inc

@@ -61,3 +61,5 @@ DIAG(warning_zero_sized_fragment_for_non_zero_symbol, DiagnosticEngine::Warning,
      "Zero sized fragment %0 for non zero sized symbol %1 from input file %2")
 DIAG(error_offset_not_assigned_for_output_section, DiagnosticEngine::Error,
      "Requested offset for output section %0 has not yet been assigned")
+DIAG(warn_empty_segment, DiagnosticEngine::Warning,
+     "Empty segment: '%0'")

include/eld/Target/GNULDBackend.h

@@ -944,6 +944,8 @@ class GNULDBackend {
   // --------------------------Provide target specific symbol values -------
   void resolveTargetDefinedSymbols();
 
+  bool verifySegments() const;
+
 private:
   // Reserved segments.
   int32_t m_NumReservedSegments = 0;

lib/Target/GNULDBackend.cpp

@@ -4034,6 +4034,8 @@ bool GNULDBackend::relax() {
     return config().getDiagEngine()->diagnose();
   }
 
+  verifySegments();
+
   return config().getDiagEngine()->diagnose();
 }
 
@@ -5169,3 +5171,12 @@ bool GNULDBackend::allocateHeaders() {
   }
   return false;
 }
+
+bool GNULDBackend::verifySegments() const {
+  const auto &SegTable = elfSegmentTable();
+  for (const auto &S : SegTable.segments()) {
+    if (S->empty())
+      config().raise(Diag::warn_empty_segment) << S->name();
+  }
+  return true;
+}

test/Common/standalone/linkerscript/WarnEmptySegment/Inputs/1.c

@@ -0,0 +1,3 @@
+int foo() { return 1; }
+
+int var = 3;

test/Common/standalone/linkerscript/WarnEmptySegment/Inputs/script.t

@@ -0,0 +1,9 @@
+PHDRS {
+  A PT_LOAD;
+  B PT_LOAD;
+}
+
+SECTIONS {
+  .text : { *(.text*) } :B
+  .data : { *(.data*) }
+}

test/Common/standalone/linkerscript/WarnEmptySegment/WarnEmptySegment.test

@@ -0,0 +1,10 @@
+#---WarnEmptySegments.test--------------------- Executable,LS------------------#
+#BEGIN_COMMENT
+# This tests checks that the linker emits a warning for empty segments.
+#END_COMMENT
+#START_TEST
+RUN: %clang %clangopts -o %t1.1.o -c %p/Inputs/1.c
+RUN: %link %linkopts -o %t1.1.out %t1.1.o -T %p/Inputs/script.t 2>&1 | %filecheck %s
+#END_TEST
+
+CHECK:  Warning: Empty segment: 'A'