Fix : gh #130 : Use -O0 not -o0 to set optimisation level for TARGET=linux

[Ulrond]

Fixes #130

Applies the patch supplied by @looopTools in the issue, with authorship preserved via git am.

-o0 is not an optimisation flag — lowercase -o is "write output to this file", so -o0 asks for a file named 0. The TARGET=linux default is now -O0.

CC ?= gcc -ggdb -O0 -Wall

TARGET=arm is untouched — it takes $(CC) from the SDK and never carried the flag.

Note for reviewers: this line is currently a no-op

Worth flagging while the line is under the microscope — Makefile:117 uses ?=, which GNU make defines as ifeq ($(origin CC),undefined). Make's built-in CC = cc has origin default, never undefined, so the assignment never fires:

$ cat probe.mk
CC ?= gcc -ggdb -O0 -Wall
show:
	@echo "CC=[$(CC)] origin=$(origin CC)"
$ make -f probe.mk show
CC=[cc] origin=default

So a standalone make TARGET=linux in ut-control compiles with bare cc — no -ggdb, no -Wall, no -O0 — and when driven from ut-core, CC arrives on the command line and overrides the line regardless. This PR is therefore a correctness fix with no behavioural change on its own.

The real -o0 damage came from ut-core passing CC="gcc -ggdb -o0 -Wall" down to this sub-make; that side is fixed in rdkcentral/ut-core#258.

If maintainers want the intended defaults to actually apply, the idiom that works while still honouring environment and command-line overrides is:

ifeq ($(origin CC),default)
CC := gcc -ggdb -O0 -Wall
endif

Deliberately left out of this PR — happy to raise it separately if wanted.

Verification

• grep -rn '\-o0' --include=Makefile --include=*.mk --include=*.sh . returns no hits.
• Standalone make TARGET=linux on this branch builds clean, and no file named 0 appears in the tree afterwards.

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Second commit: a regression guard in the tests suite

The typo is two characters, but it survived because no functional test could ever have caught it — gcc accepted -o0, a later -o $@ on the same command line won, and -O0 is gcc's default. Every build stayed green. Only a static check on the build files can see it.

tests/check_makefile_flags.py is wired into the suite as check_makefile_flags and runs before build.sh, so a flag typo costs seconds rather than a full build. It walks every Makefile/*.mk/*.sh for a lowercase -o glued to an optimisation level (-o0, -os, -og, -ofast), skipping third-party trees. Comments are stripped before matching, so prose describing the typo does not trip the check.

Verified by reintroducing -o0 on top of the fix:

Mistyped optimisation flags:
Makefile:117: CC ?= gcc -ggdb -o0 -Wall ❌
Lowercase -o names an output file. Optimisation is -O.

Build files scanned under .. :: 9
Mistyped optimisation flags :: 1
make: *** [Makefile:90: check_makefile_flags] Error 1

On the fixed tree: 9 build files scanned, 0 findings.

The value assertion is deliberately left off

The script also supports asserting what a variable actually expands to via make printenv — --expect CC=-ggdb,-O0,-Wall — which is the stronger check, since it catches flags being dropped as well as mistyped. It is not wired up here, because it would fail immediately: CC ?= never fires (see above), so CC expands to bare cc. Turning it on therefore means deciding the ?= question first. The reason is recorded in a comment in tests/Makefile next to the target so the next person does not have to rediscover it.

The same script is added to ut-core in rdkcentral/ut-core#258, where the value assertion is enabled (COMPILER and UT_CONTROL_COMPILER must contain -ggdb -O0 -Wall).

[github-actions]

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[Copilot]

Pull request overview

Updates the linux-target build defaults in ut-control’s Makefile to use the correct GCC optimization flag (-O0 instead of -o0) when setting the default CC command.

Changes:

• Fixes the linux default compiler flags to use -O0 (optimization level 0) rather than -o0 (output file option).

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

[looopTools]

I have read the CLA Document and I hereby sign the CLA