fix issue 18981: SIGSEGV during backtrace when debug info is compressed

src/core/sys/dragonflybsd/sys/elf_common.d

@@ -389,6 +389,7 @@ enum SHF_LINK_ORDER =       (1 << 7);
 enum SHF_OS_NONCONFORMING = (1 << 8);
 enum SHF_GROUP =            (1 << 9);
 enum SHF_TLS =              (1 << 10);
+enum SHF_COMPRESSED =       (1 << 11);
 
 enum SHF_MASKOS =           0x0ff00000;
 enum SHF_MASKPROC =         0xf0000000;

src/core/sys/freebsd/sys/elf_common.d

@@ -265,6 +265,7 @@ enum SHF_LINK_ORDER =       (1 << 7);
 enum SHF_OS_NONCONFORMING = (1 << 8);
 enum SHF_GROUP =            (1 << 9);
 enum SHF_TLS =              (1 << 10);
+enum SHF_COMPRESSED =       (1 << 11);
 enum SHF_MASKOS =           0x0ff00000;
 enum SHF_MASKPROC =         0xf0000000;
 

src/core/sys/linux/elf.d

@@ -314,6 +314,7 @@ enum SHF_LINK_ORDER =       (1 << 7);
 enum SHF_OS_NONCONFORMING = (1 << 8);
 enum SHF_GROUP =            (1 << 9);
 enum SHF_TLS =              (1 << 10);
+enum SHF_COMPRESSED =       (1 << 11);
 enum SHF_MASKOS =           0x0ff00000;
 enum SHF_MASKPROC =         0xf0000000;
 enum SHF_ORDERED =          (1 << 30);

src/rt/backtrace/elf.d

@@ -52,6 +52,9 @@ struct Image
         if (dbgSectionIndex != -1)
         {
             auto dbgSectionHeader = ElfSectionHeader(&file, dbgSectionIndex);
+            // we don't support compressed debug sections
+            if ((dbgSectionHeader.shdr.sh_flags & SHF_COMPRESSED) != 0)
+                return null;
             // debug_line section found and loaded
             return ElfSection(&file, &dbgSectionHeader);
         }