Add an off-by-default option to enable testing for gdb pretty printers.

[saugustine]

Summary

The current version of the pretty printers are not python3 compatible,
so turn them off by default until sufficiently improved.

[echristo]

SGTM. Thanks.

-eric

[MaskRay]

I think the latest code is Python 3 compatible. The problem is that STL on some platforms have different behaviors.

http://lab.llvm.org:8011/builders/libcxx-libcxxabi-libunwind-armv7-linux/builds/1050/steps/test.libcxx/logs/FAIL%3A%20libc%2B%2B%3A%3Agdb_pretty_printer_test.sh.cpp

GDB printed:
   'std::bitset<15> = {[2] = 1, [3] = 1, [4] = 1, [5] = 1, [6] = 1, [7] = 1, [8] = 1, [9] = 1, [10] = 1, [11] = 1, [12] = 1, [13] = 1, [14] = 1, [15] = 1, [16] = 1, [17] = 1, [18] = 1, [19] = 1, [20] = 1, [21] = 1, [22] = 1, [23] = 1, [24] = 1, [25] = 1, [26] = 1, [27] = 1, [28] = 1, [29] = 1, [30] = 1, [31] = 1, [32] = 1, [33] = 1, [34] = 1, [35] = 1, [36] = 1, [37] = 1, [38] = 1, [39] = 1, [40] = 1, [41] = 1, [42] = 1, [43] = 1, [44] = 1, [45] = 1, [46] = 1, [47] = 1, [48] = 1, [49] = 1, [50] = 1, [51] = 1, [52] = 1, [53] = 1, [54] = 1, [55] = 1, [56] = 1, [57] = 1, [58] = 1, [59] = 1, [60] = 1, [61] = 1, [62] = 1, [63] = 1, [64] = 1, [65] = 1, [66] = 1, [67] = 1, [68] = 1, [69] = 1, [70] = 1, [71] = 1, [72] = 1, [73] = 1, [74] = 1, [75] = 1, [76] = 1, [77] = 1, [78] = 1, [79] = 1, [80] = 1, [81] = 1, [82] = 1, [83] = 1, [84] = 1, [85] = 1, [86] = 1, [87] = 1, [88] = 1, [89] = 1, [90] = 1, [91] = 1, [92] = 1, [93] = 1, [94] = 1, [95] = 1, [96] = 1, [97] = 1, [98] = 1, [99] = 1, [100] = 1, [101] = 1, [102] = 1, [103] = 1, [104] = 1, [105] = 1, [106] = 1, [107] = 1, [108] = 1, [109] = 1, [110] = 1, [111] = 1, [112] = 1, [113] = 1, [114] = 1, [115] = 1, [116] = 1, [117] = 1, [118] = 1, [119] = 1, [120] = 1, [121] = 1, [122] = 1, [123] = 1, [124] = 1, [125] = 1, [126] = 1, [127] = 1, [128] = 1, [129] = 1, [130] = 1, [131] = 1, [132] = 1, [133] = 1, [134] = 1, [135] = 1, [136] = 1, [137] = 1, [138] = 1, [139] = 1, [140] = 1, [141] = 1, [142] = 1, [143] = 1, [144] = 1, [145] = 1, [146] = 1, [147] = 1, [148] = 1, [149] = 1, [150] = 1, [151] = 1, [152] = 1, [153] = 1, [154] = 1, [155] = 1, [156] = 1, [157] = 1, [158] = 1, [159] = 1, [160] = 1, [161] = 1, [162] = 1, [163] = 1, [164] = 1, [165] = 1, [166] = 1, [167] = 1, [168] = 1, [169] = 1, [170] = 1, [171] = 1, [172] = 1, [173] = 1, [174] = 1, [175] = 1, [176] = 1, [177] = 1, [178] = 1, [179] = 1, [180] = 1, [181] = 1, [182] = 1, [183] = 1, [184] = 1, [185] = 1, [186] = 1, [187] = 1, [188] = 1, [189] = 1, [190] = 1, [191] = 1, [192] = 1, [193] = 1, [194] = 1, [195] = 1, [196] = 1, [197] = 1, [198] = 1, [199] = 1, [200] = 1, [201] = 1...}'
Value should match:
   'std::bitset<15> = {[2] = 1, [3] = 1, [4] = 1, [5] = 1, [6] = 1, [7] = 1, [8] = 1, [9] = 1}'

libcxx/CMakeLists.txt

 set(ENABLE_FILESYSTEM_DEFAULT ON)
 if (WIN32)
   set(ENABLE_FILESYSTEM_DEFAULT OFF)
 endif()
 option(LIBCXX_ENABLE_FILESYSTEM "Build filesystem as part of the main libc++ library"
     ${ENABLE_FILESYSTEM_DEFAULT})
 option(LIBCXX_INCLUDE_TESTS "Build the libc++ tests." ${LLVM_INCLUDE_TESTS})
 option(LIBCXX_ENABLE_PARALLEL_ALGORITHMS "Enable the parallel algorithms library. This requires the PSTL to be available." OFF)
+option(LIBCXX_TEST_GDB_PRETTY_PRINTERS "Test gdb pretty printers." OFF)
 
 # Benchmark options -----------------------------------------------------------
 option(LIBCXX_INCLUDE_BENCHMARKS "Build the libc++ benchmarks and their dependencies" ON)
 
 set(LIBCXX_BENCHMARK_TEST_ARGS_DEFAULT --benchmark_min_time=0.01)
 set(LIBCXX_BENCHMARK_TEST_ARGS "${LIBCXX_BENCHMARK_TEST_ARGS_DEFAULT}" CACHE STRING
     "Arguments to pass when running the benchmarks using check-cxx-benchmarks")
 

libcxx/test/CMakeLists.txt

set(LIBCXX_EXECUTOR "None" CACHE STRING
     "Executor to use when running tests.")
 
 set(AUTO_GEN_COMMENT "## Autogenerated by libcxx configuration.\n# Do not edit!")
 
 if (NOT DEFINED LIBCXX_TEST_DEPS)
   message(FATAL_ERROR "Expected LIBCXX_TEST_DEPS to be defined")
 endif()
 
+# Turn this on by default when the pretty printers are python3
+# compatible.
+if(LIBCXX_TEST_GDB_PRETTY_PRINTERS)
   find_program(LIBCXX_GDB gdb)
   if (LIBCXX_GDB)
     set(LIBCXX_GDB "${LIBCXX_GDB}")
     message(STATUS "gdb found: ${LIBCXX_GDB}")
   else()
     message(STATUS "gdb not found. Disabling dependent tests.")
   endif()
+endif()
 
 if (LIBCXX_INCLUDE_TESTS)
   include(AddLLVM) # for configure_lit_site_cfg and add_lit_testsuit
 
   configure_lit_site_cfg(
     ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.in
     ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg)