Experimental Physics and
Industrial Control System

"Dmitry Yu. Bolkhovityanov via Tech-talk" <tech-talk at aps.anl.gov> · Sun, 30 Apr 2023 12:51:55 +0700 (+07)

On Fri, 28 Apr 2023, Dmitry Yu. Bolkhovityanov via Tech-talk wrote:

 It's possible that removing the asLib$(DEP) rule might clean this up, but
 I don't know if the result will actually build. Please let me know if you
 find a solution that removes some of this complexity.

I'll try to, but I doubt I'm able to completely grok the operation of EPICS

build system.

(Shame on me, even the principle of "HOST_OPT=NO" functioning is still a

mystery: there are no references to $(HOST_OPT) besides 6 items in

*win32-x86.win32-x86 files, yet the "HOST_OPT=NO" does affect Linux builds.

Must be something with computed variable names...)

UPD: I figured out how $(HOST_OPT) works:

1. The configure/CONFIG_COMMON file specifies "BUILD_CLASS = HOST"

2. Below there are lines

# Warnings flags
WARN_CPPFLAGS = $(WARN_CPPFLAGS_$($(BUILD_CLASS)_WARN))
WARN_CFLAGS = $(WARN_CFLAGS_$($(BUILD_CLASS)_WARN))
WARN_CXXFLAGS = $(WARN_CXXFLAGS_$($(BUILD_CLASS)_WARN))

# Optimization flags
OPT_CPPFLAGS = $(OPT_CPPFLAGS_$($(BUILD_CLASS)_OPT))
OPT_CFLAGS = $(OPT_CFLAGS_$($(BUILD_CLASS)_OPT))
OPT_CXXFLAGS = $(OPT_CXXFLAGS_$($(BUILD_CLASS)_OPT))

3. Specific CONFIG.* files define OPT_nnn_YES и OPT_nnn_NO, e.g.

configure/CONFIG.gnuCommon sets

OPT_CFLAGS_YES = -O3
OPT_CFLAGS_NO = -g

4. Thus, setting HOST_OPT=YES or HOST_OPT=NO selects which of OPT_CFLAGS_*

to use.

Well, that's an elegant albeit a rather non-obvoius implementation.

It's a pity this isn't described somewhere in documentation. Computed

variable names, while giving much flexibility, are extremely tricky and

turn Makefiles into difficult to study, plus "double-indirect" references

entangle things even more (you can't find anything until you know exactly

what to find).

With best regards,
Dmitry

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System