Reducing Warnings - Compile with C99 on Evergreen by default (#1067)

* CDRIVER-4136 Use -std=c99 by default for all compilation on Evergreen

* Fix compatiblity issues with glibc versions 2.19 and earlier

* Remove debug-compile-c99 task from Evergreen

Author: eramongodb

.evergreen/compile-unix.sh

@@ -4,6 +4,7 @@ set -o errexit  # Exit the script with error if any of the commands fail
 # Supported/used environment variables:
 # Options for this script:
 #       CFLAGS                  Additional compiler flags
+#       C_STD_VERSION           C standard version to compile with (default: 99)
 #       MARCH                   Machine Architecture. Defaults to lowercase uname -m
 #       RELEASE                 Use the fully qualified release archive
 #       DEBUG                   Use debug configure flags
@@ -28,6 +29,7 @@ set -o errexit  # Exit the script with error if any of the commands fail
 #       ZSTD                    Build against system zstd.
 
 # Options for this script.
+C_STD_VERSION=${CSTD_VERSION:-99}
 RELEASE=${RELEASE:-OFF}
 DEBUG=${DEBUG:-OFF}
 TRACING=${TRACING:-OFF}
@@ -46,6 +48,7 @@ ZLIB=${ZLIB:-BUNDLED}
 INSTALL_DIR=$(pwd)/install-dir
 
 echo "CFLAGS: $CFLAGS"
+echo "C_STD_VERSION: $C_STD_VERSION"
 echo "SANITIZE: $SANITIZE"
 echo "MARCH: $MARCH"
 echo "RELEASE: $RELEASE"
@@ -163,6 +166,8 @@ export ASAN_OPTIONS="detect_leaks=1 abort_on_error=1 symbolize=1"
 export ASAN_SYMBOLIZER_PATH="/opt/mongodbtoolchain/v3/bin/llvm-symbolizer"
 export TSAN_OPTIONS="suppressions=./.tsan-suppressions"
 
+CONFIGURE_FLAGS="$CONFIGURE_FLAGS -DCMAKE_C_STANDARD=$C_STD_VERSION -DCMAKE_C_STANDARD_REQUIRED=ON -DCMAKE_C_EXTENSIONS=OFF"
+
 case "$MARCH" in
    i386)
       CFLAGS="$CFLAGS -m32 -march=i386"

.evergreen/compile-windows.sh

@@ -4,6 +4,7 @@ set -o errexit  # Exit the script with error if any of the commands fail
 
 # Supported/used environment variables:
 #  CC              Which compiler to use
+#  C_STD_VERSION   C standard version to compile with (default: c99)
 #  SSL             OPENSSL, OPENSSL_STATIC, WINDOWS, or OFF
 #  SASL            AUTO, SSPI, CYRUS, or OFF
 #  SRV             Whether to enable SRV: ON or OFF
@@ -21,10 +22,12 @@ CONFIGURE_FLAGS="\
 BUILD_FLAGS="/m"  # Number of concurrent processes. No value=# of cpus
 CMAKE="/cygdrive/c/cmake/bin/cmake"
 CC=${CC:-"Visual Studio 15 2017 Win64"}
+C_STD_VERSION=${CSTD_VERSION:-99}
 SSL=${SSL:-WINDOWS}
 SASL=${SASL:-SSPI}
 
 echo "CC: $CC"
+echo "C_STD_VERSION: $C_STD_VERSION"
 echo "RELEASE: $RELEASE"
 echo "SASL: $SASL"
 
@@ -35,6 +38,8 @@ if [ "$RELEASE" ]; then
    cd build-dir
 fi
 
+CONFIGURE_FLAGS="$CONFIGURE_FLAGS -DCMAKE_C_STANDARD=$C_STD_VERSION -DCMAKE_C_STANDARD_REQUIRED=ON -DCMAKE_C_EXTENSIONS=OFF"
+
 CONFIGURE_FLAGS="$CONFIGURE_FLAGS -DENABLE_SASL=$SASL"
 
 case "$SSL" in

.evergreen/config.yml

@@ -1030,26 +1030,7 @@ tasks:
       shell: bash
       script: |-
         set -o errexit
-        export CFLAGS="-std=c11"
-        export DEBUG="ON"
-        export SANITIZE=""
-        CC='${CC}' MARCH='${MARCH}' sh .evergreen/compile.sh
-  - func: upload build
-- name: debug-compile-c99
-  tags:
-  - c99
-  - debug-compile
-  - special
-  - stdflags
-  commands:
-  - command: shell.exec
-    type: test
-    params:
-      working_dir: mongoc
-      shell: bash
-      script: |-
-        set -o errexit
-        export CFLAGS="-std=c99"
+        export C_STD_VERSION="11"
         export DEBUG="ON"
         export SANITIZE=""
         CC='${CC}' MARCH='${MARCH}' sh .evergreen/compile.sh

CMakeLists.txt

@@ -243,10 +243,21 @@ set (CMAKE_MACOSX_RPATH ON)
 # silence a CMake 3.11 warning that the old behavior is deprecated.
 cmake_policy (SET CMP0042 NEW)
 
-# https://www.gnu.org/software/libc/manual/html_node/Feature-Test-Macros.html
-# Enable features from POSIX.1-2008 as well as certain BSD and SVID features.
-add_definitions (-D_DEFAULT_SOURCE)
-list (APPEND CMAKE_REQUIRED_DEFINITIONS -D_DEFAULT_SOURCE)
+# https://man7.org/linux/man-pages/man7/feature_test_macros.7.html
+# https://pubs.opengroup.org/onlinepubs/7908799/xsh/compilation.html
+# Enable POSIX features up to POSIX.1-2008 plus the XSI extension and BSD-derived definitions.
+# Both _BSD_SOURCE and _DEFAULT_SOURCE are defined for backwards-compatibility with glibc 2.19 and earlier.
+# _BSD_SOURCE and _DEFAULT_SOURCE are required by `getpagesize`, `h_errno`, etc.
+# _XOPEN_SOURCE=700 is required by `strnlen`, etc.
+add_definitions (-D_XOPEN_SOURCE=700 -D_BSD_SOURCE -D_DEFAULT_SOURCE)
+list (APPEND CMAKE_REQUIRED_DEFINITIONS -D_XOPEN_SOURCE=700 -D_BSD_SOURCE -D_DEFAULT_SOURCE)
+
+# https://opensource.apple.com/source/Libc/Libc-1439.40.11/gen/compat.5.auto.html
+# Non-POSIX extensions are required by `_SC_NPROCESSORS_ONLN`.
+if (CMAKE_SYSTEM_NAME MATCHES "Darwin")
+   add_definitions (-D_DARWIN_C_SOURCE)
+   list (APPEND CMAKE_REQUIRED_DEFINITIONS -D_DARWIN_C_SOURCE)
+endif ()
 
 add_subdirectory (src/common)
 

build/evergreen_config_lib/tasks.py

@@ -198,10 +198,7 @@ def __init__(self, task_name, suffix_commands, orchestration=True, **kwargs):
     CompileTask('debug-compile-lto-thin', CFLAGS='-flto=thin'),
     SpecialTask('debug-compile-c11',
                 tags=['debug-compile', 'c11', 'stdflags'],
-                CFLAGS='-std=c11'),
-    SpecialTask('debug-compile-c99',
-                tags=['debug-compile', 'c99', 'stdflags'],
-                CFLAGS='-std=c99'),
+                C_STD_VERSION='11'),
     SpecialTask('debug-compile-valgrind',
                 tags=['debug-compile', 'valgrind'],
                 SASL='OFF',