BUILD: Makefile: speed up compiler options detection

Commits b78016649 and d3a7f4035 brought the ability to detect the build
options and warnings that the compiler supports. However, they're detected
using "$(CC) -c", which is 50% slower than "$(CC) -E" for the same result,
just because it starts the assembler at the end. Given that we're starting
to check for a number of warnings, this detection alone starts to become
visible, taking a bit more than 300 ms on the build time. Let's switch to
-E instead to shrink this incompressible time by roughly 100 ms.
This commit is contained in:
Willy Tarreau 2018-10-03 09:52:51 +02:00
parent a8b12c6bb7
commit f11ca5e7a4

View File

@ -102,13 +102,13 @@
# Usage: CFLAGS += $(call cc-opt,option). Eg: $(call cc-opt,-fwrapv)
# Note: ensure the referencing variable is assigned using ":=" and not "=" to
# call it only once.
cc-opt = $(shell set -e; if $(CC) $(1) -c -xc - -o /dev/null </dev/null >&0 2>&0; then echo "$(1)"; fi;)
cc-opt = $(shell set -e; if $(CC) $(1) -E -xc - -o /dev/null </dev/null >&0 2>&0; then echo "$(1)"; fi;)
# Disable a warning when supported by the compiler. Don't put spaces around the
# warning! And don't use cc-opt which doesn't always report an error until
# another one is also returned.
# Usage: CFLAGS += $(call cc-nowarn,warning). Eg: $(call cc-opt,format-truncation)
cc-nowarn = $(shell set -e; if $(CC) -W$(1) -c -xc - -o /dev/null </dev/null >&0 2>&0; then echo "-Wno-$(1)"; fi;)
cc-nowarn = $(shell set -e; if $(CC) -W$(1) -E -xc - -o /dev/null </dev/null >&0 2>&0; then echo "-Wno-$(1)"; fi;)
#### Installation options.
DESTDIR =