LV2 atoms are misaligned

[Valtteri Kallinen]

If the LV2 MIDI example plugins are built using:

clang -fno-omit-frame-pointer -g -fsanitize=undefined -shared-libasan <plugin>.c -shared -fPIC -o <plugin>.so

then running Carla using:

LD_PRELOAD=$(clang -print-file-name=libclang_rt.ubsan_standalone.so)

gives the following runtime errors:

src/eg-fifths.lv2/fifths.c:103:13: runtime error: member access within misaligned address 0x55555747058c for type 'LV2_Atom_Event', which requires 8 byte alignment
0x55555747058c: note: pointer points here
  60 05 47 57 00 00 00 00  00 00 00 00 03 00 00 00  2f 00 00 00 90 4a 64 00  11 00 00 00 08 00 00 00
              ^ 
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior src/eg-fifths.lv2/fifths.c:103:13 
src/eg-fifths.lv2/fifths.c:103:13: runtime error: member access within misaligned address 0x555557470594 for type 'LV2_Atom', which requires 8 byte alignment
0x555557470594: note: pointer points here
  00 00 00 00 03 00 00 00  2f 00 00 00 90 4a 64 00  11 00 00 00 08 00 00 00  70 69 70 65 77 69 72 65
              ^ 
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior src/eg-fifths.lv2/fifths.c:103:13 
/usr/include/lv2/atom/util.h:171:65: runtime error: member access within misaligned address 0x55555747058c for type 'const LV2_Atom_Event', which requires 8 byte alignment
0x55555747058c: note: pointer points here
  60 05 47 57 00 00 00 00  00 00 00 00 03 00 00 00  2f 00 00 00 90 4a 64 00  11 00 00 00 08 00 00 00
              ^ 
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/include/lv2/atom/util.h:171:65 
/usr/include/lv2/atom/util.h:171:65: runtime error: member access within misaligned address 0x555557470594 for type 'const LV2_Atom', which requires 8 byte alignment
0x555557470594: note: pointer points here
  00 00 00 00 03 00 00 00  2f 00 00 00 90 4a 64 00  11 00 00 00 08 00 00 00  70 69 70 65 77 69 72 65
              ^ 
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/include/lv2/atom/util.h:171:65 
/usr/include/lv2/atom/util.h:171:70: runtime error: load of misaligned address 0x555557470594 for type 'const uint32_t' (aka 'const unsigned int'), which requires 8 byte alignment
0x555557470594: note: pointer points here
  00 00 00 00 03 00 00 00  2f 00 00 00 90 4a 64 00  11 00 00 00 08 00 00 00  70 69 70 65 77 69 72 65
              ^ 
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/include/lv2/atom/util.h:171:70 
/usr/include/lv2/atom/util.h:177:10: runtime error: store to misaligned address 0x55555747270c for type 'LV2_Atom_Event *', which requires 8 byte alignment
0x55555747270c: note: pointer points here
  e0 26 47 57 55 55 00 00  3a 49 6e 74 65 72 66 61  63 65 3a 46 61 63 74 6f  72 79 00 00 00 00 00 00
              ^ 
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /usr/include/lv2/atom/util.h:177:10 

The bug does not occur with Jalv or Reaper. The LV2 atoms should be 64-bit aligned.

http://lv2plug.in/ns/ext/atom#Atom
https://lv2plug.in/c/html/group__atom.html#structLV2__Atom__Sequence__Body