[Lldb-commits] [lldb] r353280 - Fix strlen() of unbound array undefined behavior

[Jan Kratochvil via lldb-commits]

Author: jankratochvil
Date: Wed Feb  6 00:44:13 2019
New Revision: 353280

URL: http://llvm.org/viewvc/llvm-project?rev=353280&view=rev
Log:
Fix strlen() of unbound array undefined behavior

LLDB testsuite fails when built by GCC8 on:
  LLDB :: SymbolFile/DWARF/find-basic-namespace.cpp

This is because this code in LLDB codebase has undefined behavior:

  #include <algorithm>
  #include <string.h>
  // lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp:1731
  static struct section_64 {
    char sectname[16];
    char segname[16];
  } sect64 = { {'_','_','a','p','p','l','e','_','n','a','m','e','s','p','a','c'}, "__DWARF" };
  int main() {
    return std::min<size_t>(strlen(sect64.sectname), sizeof(sect64.sectname));
  }

It has been discussed as a (false) bugreport to GCC:
  wrong-code: LLDB testcase fails: SymbolFile/DWARF/find-basic-namespace.cpp
  https://bugzilla.redhat.com/show_bug.cgi?id=1672436

Differential Revision: https://reviews.llvm.org/D57781

Modified:
    lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
    lldb/trunk/source/Utility/ConstString.cpp

Modified: lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp?rev=353280&r1=353279&r2=353280&view=diff
==============================================================================
--- lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp (original)
+++ lldb/trunk/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp Wed Feb  6 00:44:13 2019
@@ -1609,8 +1609,7 @@ void ObjectFileMachO::ProcessSegmentComm
   bool add_section = true;
   bool add_to_unified = true;
   ConstString const_segname(
-      load_cmd.segname,
-      std::min<size_t>(strlen(load_cmd.segname), sizeof(load_cmd.segname)));
+      load_cmd.segname, strnlen(load_cmd.segname, sizeof(load_cmd.segname)));
 
   SectionSP unified_section_sp(
       context.UnifiedList.FindSectionByName(const_segname));
@@ -1729,8 +1728,7 @@ void ObjectFileMachO::ProcessSegmentComm
 
     if (add_section) {
       ConstString section_name(
-          sect64.sectname,
-          std::min<size_t>(strlen(sect64.sectname), sizeof(sect64.sectname)));
+          sect64.sectname, strnlen(sect64.sectname, sizeof(sect64.sectname)));
       if (!const_segname) {
         // We have a segment with no name so we need to conjure up segments
         // that correspond to the section's segname if there isn't already such

Modified: lldb/trunk/source/Utility/ConstString.cpp
URL: http://llvm.org/viewvc/llvm-project/lldb/trunk/source/Utility/ConstString.cpp?rev=353280&r1=353279&r2=353280&view=diff
==============================================================================
--- lldb/trunk/source/Utility/ConstString.cpp (original)
+++ lldb/trunk/source/Utility/ConstString.cpp Wed Feb  6 00:44:13 2019
@@ -143,7 +143,7 @@ public:
   const char *GetConstTrimmedCStringWithLength(const char *cstr,
                                                size_t cstr_len) {
     if (cstr != nullptr) {
-      const size_t trimmed_len = std::min<size_t>(strlen(cstr), cstr_len);
+      const size_t trimmed_len = strnlen(cstr, cstr_len);
       return GetConstCStringWithLength(cstr, trimmed_len);
     }
     return nullptr;