configure: Always compile with -fwrapv

QEMU's code relies on left shifts of signed integers always
being defined behaviour with the obvious 2s-complement
semantics. The only way to tell the compiler (and any
associated undefined-behaviour sanitizer) that we require a
C dialect with these semantics is to use the -fwrapv option.
This is a bit of a heavy hammer for the job as it also gives
us guaranteed semantics on integer arithmetic overflow which
in theory we don't require.

In an ideal world this would allow us to drop the warning
flag -Wno-shift-negative-value, but we must retain this to
avoid spurious warnings on clang versions predating the
fix to https://llvm.org/bugs/show_bug.cgi?id=25552.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1473685808-9629-1-git-send-email-peter.maydell@linaro.org
1 file changed
tree: 4f91fdf1fe6cec0f9294d6d8013e556f16d87676
  1. audio/
  2. backends/
  3. block/
  4. bsd-user/
  5. contrib/
  6. crypto/
  7. default-configs/
  8. disas/
  9. docs/
  10. fpu/
  11. fsdev/
  12. gdb-xml/
  13. hw/
  14. include/
  15. io/
  16. libdecnumber/
  17. linux-headers/
  18. linux-user/
  19. migration/
  20. nbd/
  21. net/
  22. pc-bios/
  23. po/
  24. qapi/
  25. qga/
  26. qobject/
  27. qom/
  28. replay/
  29. roms/
  30. scripts/
  31. slirp/
  32. stubs/
  33. target-alpha/
  34. target-arm/
  35. target-cris/
  36. target-i386/
  37. target-lm32/
  38. target-m68k/
  39. target-microblaze/
  40. target-mips/
  41. target-moxie/
  42. target-openrisc/
  43. target-ppc/
  44. target-s390x/
  45. target-sh4/
  46. target-sparc/
  47. target-tilegx/
  48. target-tricore/
  49. target-unicore32/
  50. target-xtensa/
  51. tcg/
  52. tests/
  53. trace/
  54. ui/
  55. util/
  56. .dir-locals.el
  57. .exrc
  58. .gitignore
  59. .gitmodules
  60. .mailmap
  61. .travis.yml
  62. accel.c
  63. aio-posix.c
  64. aio-win32.c
  65. arch_init.c
  66. async.c
  67. balloon.c
  68. block.c
  69. blockdev-nbd.c
  70. blockdev.c
  71. blockjob.c
  72. bootdevice.c
  73. bt-host.c
  74. bt-vhci.c
  75. Changelog
  76. CODING_STYLE
  77. configure
  78. COPYING
  79. COPYING.LIB
  80. cpu-exec-common.c
  81. cpu-exec.c
  82. cpus.c
  83. cputlb.c
  84. device-hotplug.c
  85. device_tree.c
  86. disas.c
  87. dma-helpers.c
  88. dump.c
  89. exec.c
  90. gdbstub.c
  91. HACKING
  92. hmp-commands-info.hx
  93. hmp-commands.hx
  94. hmp.c
  95. hmp.h
  96. iohandler.c
  97. ioport.c
  98. iothread.c
  99. kvm-all.c
  100. kvm-stub.c
  101. LICENSE
  102. main-loop.c
  103. MAINTAINERS
  104. Makefile
  105. Makefile.objs
  106. Makefile.target
  107. memory.c
  108. memory_mapping.c
  109. module-common.c
  110. monitor.c
  111. numa.c
  112. os-posix.c
  113. os-win32.c
  114. page_cache.c
  115. qapi-schema.json
  116. qdev-monitor.c
  117. qdict-test-data.txt
  118. qemu-bridge-helper.c
  119. qemu-char.c
  120. qemu-doc.texi
  121. qemu-ga.texi
  122. qemu-img-cmds.hx
  123. qemu-img.c
  124. qemu-img.texi
  125. qemu-io-cmds.c
  126. qemu-io.c
  127. qemu-nbd.c
  128. qemu-nbd.texi
  129. qemu-option-trace.texi
  130. qemu-options-wrapper.h
  131. qemu-options.h
  132. qemu-options.hx
  133. qemu-seccomp.c
  134. qemu-tech.texi
  135. qemu-timer.c
  136. qemu.nsi
  137. qemu.sasl
  138. qmp-commands.hx
  139. qmp.c
  140. qtest.c
  141. README
  142. replication.c
  143. replication.h
  144. rules.mak
  145. softmmu_template.h
  146. spice-qemu-char.c
  147. tcg-runtime.c
  148. tci.c
  149. thread-pool.c
  150. thunk.c
  151. tpm.c
  152. trace-events
  153. translate-all.c
  154. translate-all.h
  155. translate-common.c
  156. user-exec.c
  157. VERSION
  158. version.rc
  159. vl.c
  160. xen-common-stub.c
  161. xen-common.c
  162. xen-hvm-stub.c
  163. xen-hvm.c
  164. xen-mapcache.c