master 5013065 2/4: Speed up GCC 10.1 compilation in default Git builds

[Paul Eggert]

branch: master
commit 501306557c6bb65007f384aa203999d1577d0e99
Author: Paul Eggert <eggert@cs.ucla.edu>
Commit: Paul Eggert <eggert@cs.ucla.edu>

    Speed up GCC 10.1 compilation in default Git builds
    
    * configure.ac (nw): GCC 10.1 introduced warnings enabled by -fanalyzer
    that slow down compilation considerably.  Generate these warnings only
    if --enable-gcc-warnings is explicitly given.  Also, do not bother to
    eliminate warnings that Gnulib’s revised manywarnings module no longer
    generates.
---
 configure.ac | 26 +++++++-------------------
 1 file changed, 7 insertions(+), 19 deletions(-)

diff --git a/configure.ac b/configure.ac
index 6ede610..9fe1a0d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1030,14 +1030,17 @@ AS_IF([test $gl_gcc_warnings = no],
        ;;
   esac
   AS_IF([test $gl_gcc_warnings = yes],
-    [WERROR_CFLAGS=-Werror])
+    [WERROR_CFLAGS=-Werror],
+    [# Use -fanalyzer and related options only if --enable-gcc-warnings,
+     # as they slow GCC considerably.
+     nw="$nw -fanalyzer -Wno-analyzer-double-free -Wno-analyzer-malloc-leak"
+     nw="$nw -Wno-analyzer-null-dereference -Wno-analyzer-use-after-free"])
 
-  nw="$nw -Wcast-align -Wcast-align=strict" # Emacs is tricky with pointers.
+  nw="$nw -Wcast-align=strict"      # Emacs is tricky with pointers.
   nw="$nw -Wduplicated-branches"    # Too many false alarms
   nw="$nw -Wformat-overflow=2"      # False alarms due to GCC bug 80776
   nw="$nw -Wsystem-headers"         # Don't let system headers trigger warnings
   nw="$nw -Woverlength-strings"     # Not a problem these days
-  nw="$nw -Wformat-nonliteral"      # we do this a lot
   nw="$nw -Wvla"                    # Emacs uses <vla.h>.
   nw="$nw -Wunused-const-variable=2" # lisp.h declares const objects.
   nw="$nw -Winline"                 # OK to ignore 'inline'
@@ -1046,7 +1049,6 @@ AS_IF([test $gl_gcc_warnings = no],
   nw="$nw -Wsync-nand"              # irrelevant here, and provokes ObjC 
warning
   nw="$nw -Wunsafe-loop-optimizations" # OK to suppress unsafe optimizations
   nw="$nw -Wbad-function-cast"      # These casts are no worse than others.
-  nw="$nw -Wabi"                    # Not useful, perceived as noise
 
   # Emacs doesn't care about shadowing; see
   # <https://lists.gnu.org/r/emacs-diffs/2011-11/msg00265.html>.
@@ -1066,26 +1068,12 @@ AS_IF([test $gl_gcc_warnings = no],
   # option problematic.
   nw="$nw -Wsuggest-attribute=pure"
 
-  # This part is merely for shortening the command line,
-  # since -Wall implies -Wswitch.
-  nw="$nw -Wswitch"
-
-  # This part is merely for shortening the command line,
-  # since -Wno-FOO needs to be added below regardless.
-  nw="$nw -Wmissing-field-initializers"
-  nw="$nw -Woverride-init"
-  nw="$nw -Wtype-limits"
-  nw="$nw -Wunused-parameter"
-
   if test "$emacs_cv_clang" = yes; then
-    nw="$nw -Wcast-align"
     nw="$nw -Wdouble-promotion"
-    nw="$nw -Wmissing-braces"
   fi
 
-  # These cause too much noise in the MinGW build
+  # This causes too much noise in the MinGW build.
   if test $opsys = mingw32; then
-    nw="$nw -Wpointer-sign"
     nw="$nw -Wsuggest-attribute=format"
   fi