feat(build): add 'CONSERVE_MEMORY' cmake option

When CONSERVE_MEMORY=ON and gcc is being used, we provide additional
command line options that will minimize the amount of memory used by gcc
when compiling Lean.
This is an attempt to fix the "out-of-memory" failures when building
Lean at Travis.

.travis.yml

@@ -23,6 +23,7 @@ env:
      PUSH_TO_CDASH=TRUE
      TCMALLOC=OFF
      LUA=52
+     CONSERVE_MEMORY=ON
    # =======================================================
    # DEBUG Build
    # =======================================================
@@ -41,6 +42,7 @@ env:
      TCMALLOC=ON
      PUSH_TO_CDASH=TRUE
      LUA=52
+     CONSERVE_MEMORY=ON
    # D3. clang++-3.3 | DEBUG
    - CMAKE_CXX_COMPILER=clang++-3.3
      CMAKE_BUILD_TYPE=DEBUG
@@ -53,6 +55,7 @@ env:
      TCMALLOC=OFF
      PUSH_TO_CDASH=TRUE
      LUA=52
+     CONSERVE_MEMORY=ON
    # =======================================================
    # RELEASE Build
    # =======================================================
@@ -70,6 +73,7 @@ env:
      PUSH_TO_CDASH=TRUE
      LUA=52
      PACKAGE=TRUE
+     CONSERVE_MEMORY=ON
    # R3. clang++-3.3 | RELEASE
    - CMAKE_CXX_COMPILER=clang++-3.3
      CMAKE_BUILD_TYPE=RELEASE
@@ -83,6 +87,7 @@ env:
      UPLOAD=linux
      PUSH_TO_CDASH=TRUE
      LUA=52
+     CONSERVE_MEMORY=ON
    # =======================================================
    # MEMCHECK Build
    # =======================================================
@@ -110,6 +115,7 @@ env:
      MEMCHECK_RANGE=1,40
      PUSH_TO_CDASH=TRUE
      LUA=52
+     CONSERVE_MEMORY=ON
     # M2-2. g++-4.8     | DEBUG    | MEMCHECK       | CDASH
    - CMAKE_CXX_COMPILER=g++-4.8
      CMAKE_BUILD_TYPE=DEBUG
@@ -118,6 +124,7 @@ env:
      MEMCHECK_RANGE=40,80
      PUSH_TO_CDASH=TRUE
      LUA=52
+     CONSERVE_MEMORY=ON
    # =======================================================
    # DOXYGEN Build
    # =======================================================
@@ -127,6 +134,7 @@ env:
      BUILD_DOXYGEN=TRUE
      TCMALLOC=OFF
      LUA=52
+     CONSERVE_MEMORY=ON
    # =======================================================
    # Different Lua Versions
    # =======================================================
@@ -137,6 +145,7 @@ env:
      UPLOAD=linux
      PUSH_TO_CDASH=TRUE
      LUA=51
+     CONSERVE_MEMORY=ON
    # LJIT. g++-4.8     | RELEASE |                | CDASH
    - CMAKE_CXX_COMPILER=g++-4.8
      CMAKE_BUILD_TYPE=RELEASE
@@ -144,6 +153,7 @@ env:
      UPLOAD=linux
      PUSH_TO_CDASH=TRUE
      LUA=JIT
+     CONSERVE_MEMORY=ON
 
 install:
   - until sudo add-apt-repository --yes ppa:ubuntu-toolchain-r/test; do echo retry; done
@@ -230,7 +240,7 @@ script:
   - if [[ $TESTCOV != ON ]]; then
        TESTCOV=OFF;
     fi
-  - /usr/bin/cmake -DIGNORE_SORRY=ON -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} -DTESTCOV=${TESTCOV} -DTCMALLOC=${TCMALLOC} -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} ${GENERATOR} -DCMAKE_PROGRAM_PATH=/usr/bin ../src;
+  - /usr/bin/cmake -DIGNORE_SORRY=ON -DCONSERVE_MEMORY=${CONSERVE_MEMORY} -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE} -DTESTCOV=${TESTCOV} -DTCMALLOC=${TCMALLOC} -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER} ${GENERATOR} -DCMAKE_PROGRAM_PATH=/usr/bin ../src;
   - if [[ $CMAKE_BUILD_TYPE == DEBUG || $CMAKE_BUILD_TYPE == RELEASE || $TESTCOV == ON ]]; then
        SITE=Ubuntu12.04@Travis;
        if [[ $CMAKE_BUILD_TYPE == RELEASE ]]; then

src/CMakeLists.txt

@@ -27,6 +27,9 @@ option(IGNORE_SORRY       "IGNORE_SORRY"      OFF)
 # When cross-compiling, we do not compile the standard library since
 # the executable will not work on the host machine
 option(CROSS_COMPILE      "CROSS_COMPILE"     OFF)
+# When ON we try to minimize the amount of memory needed to compile Lean using gcc.
+# We use this flag when compiling at Travis.
+option(CONSERVE_MEMORY    "CONSERVE_MEMORY"   OFF)
 
 # Added for CTest
 include(CTest)
@@ -60,9 +63,14 @@ if("${CACHE_EXPRS}" MATCHES "ON")
   set(LEAN_EXTRA_CXX_FLAGS "${LEAN_EXTRA_CXX_FLAGS} -D LEAN_CACHE_EXPRS")
 endif()
 
+if(("${CONSERVE_MEMORY}" MATCHES "ON") AND ("${CMAKE_CXX_COMPILER_ID}" MATCHES "GNU"))
+  message(STATUS "Using compilation flags for minimizing the amount of memory used by gcc")
+  set(LEAN_EXTRA_CXX_FLAGS "${LEAN_EXTRA_CXX_FLAGS} --param ggc-min-heapsize=32768 --param ggc-min-expand=20")
+endif()
+
 if("${STATIC}" MATCHES "ON")
-  set(LEAN_EXTRA_LINKER_FLAGS "${LEAN_EXTRA_LINKER_FLAGS} -static")
   message(STATUS "Creating a static executable")
+  set(LEAN_EXTRA_LINKER_FLAGS "${LEAN_EXTRA_LINKER_FLAGS} -static")
 endif()
 
 # Set Module Path