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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

llvm-svn: 353280
This commit is contained in:
Jan Kratochvil 2019-02-06 08:44:13 +00:00
parent b8ee8c8517
commit bb3609e49d
2 changed files with 3 additions and 5 deletions
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6
lldb/source/Plugins/ObjectFile/Mach-O/ObjectFileMachO.cpp
View File

@ -1609,8 +1609,7 @@ void ObjectFileMachO::ProcessSegmentCommand(const load_command &load_cmd_,
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::ProcessSegmentCommand(const load_command &load_cmd_,
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

2
lldb/source/Utility/ConstString.cpp
View File

@ -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;