Unreachable code warnings while building latest main at 48c70b8

[srinivasreddy]

Bug report

Bug description:

I ran the ./configure and make, here are the warnings shown.

gcc -c -fno-strict-overflow -Wsign-compare -Wunreachable-code -DNDEBUG -g -O3 -Wall    -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal -I./Include/internal/mimalloc  -I. -I./Include    -DPy_BUILD_CORE -o Python/ast.o Python/ast.c
gcc -c -fno-strict-overflow -Wsign-compare -Wunreachable-code -DNDEBUG -g -O3 -Wall    -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal -I./Include/internal/mimalloc  -I. -I./Include    -DPy_BUILD_CORE -o Python/ast_opt.o Python/ast_opt.c
gcc -c -fno-strict-overflow -Wsign-compare -Wunreachable-code -DNDEBUG -g -O3 -Wall    -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal -I./Include/internal/mimalloc  -I. -I./Include    -DPy_BUILD_CORE -o Python/ast_unparse.o Python/ast_unparse.c
gcc -c -fno-strict-overflow -Wsign-compare -Wunreachable-code -DNDEBUG -g -O3 -Wall    -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal -I./Include/internal/mimalloc  -I. -I./Include    -DPy_BUILD_CORE -o Python/bltinmodule.o Python/bltinmodule.c
gcc -c -fno-strict-overflow -Wsign-compare -Wunreachable-code -DNDEBUG -g -O3 -Wall    -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal -I./Include/internal/mimalloc  -I. -I./Include    -DPy_BUILD_CORE -o Python/brc.o Python/brc.c
gcc -c -fno-strict-overflow -Wsign-compare -Wunreachable-code -DNDEBUG -g -O3 -Wall    -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal -I./Include/internal/mimalloc  -I. -I./Include    -DPy_BUILD_CORE -o Python/ceval.o Python/ceval.c
In file included from Python/ceval.c:904:
Python/generated_cases.c.h:808:31: warning: code will never be executed [-Wunreachable-code]
  808 |                 for (int _i = oparg; --_i >= 0;) {
      |                               ^~~~~
Python/generated_cases.c.h:694:31: warning: code will never be executed [-Wunreachable-code]
  694 |                 for (int _i = oparg*2; --_i >= 0;) {
      |                               ^~~~~
2 warnings generated.

Operating System:

➜  cpython git:(main) uname -a
Darwin SREDDY- 24.1.0 Darwin Kernel Version 24.1.0: Thu Oct 10 21:02:27 PDT 2024; root:xnu-11215.41.3~2/RELEASE_X86_64 x86_64

Main branch commit : 48c70b8

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

[srinivasreddy]

I have updated the tcl-tk to version 9.0.0_1, the warnings are gone. Please refer - build.log

[erlend-aasland]

I cannot reproduce this on my MacBook. The tcl-tk comment seems off-topic for this issue. Can you provide more information about your environment?

[srinivasreddy]

Like gcc compiler version? and ...?

[erlend-aasland]

Include everything that is needed to reproduce the failure you are seeing. Are you still seeing these failures? Did you compile from a clean source tree (git clean -fdx)?

[srinivasreddy]

➜  cpython git:(main) env
TERM_SESSION_ID=REDACTED
SSH_AUTH_SOCK=/private/tmp/com.apple.launchd.xFPWqTHwrg/Listeners
LC_TERMINAL_VERSION=3.5.10
COLORFGBG=7;0
ITERM_PROFILE=REDACTED
XPC_FLAGS=0x0
LANG=en_US.UTF-8
PWD=/Users/REDACTED/workspace/github_repos/cpython
SHELL=/bin/zsh
__CFBundleIdentifier=com.googlecode.iterm2
TERM_FEATURES=REDACTED
TERM_PROGRAM_VERSION=3.5.10
TERM_PROGRAM=iTerm.app
PATH=/Users/REDACTED/.nvm/versions/node/v20.17.0/bin:/Library/Frameworks/Python.framework/Versions/3.8/bin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/Library/Apple/usr/bin:/Users/REDACTED/.cargo/bin:/Applications/iTerm.app/Contents/Resources/utilities:/Users/REDACTED/.local/bin
LC_TERMINAL=iTerm2
COLORTERM=truecolor
COMMAND_MODE=unix2003
TERM=xterm-256color
TERMINFO_DIRS=/Applications/iTerm.app/Contents/Resources/terminfo:/usr/share/terminfo
HOME=/Users/REDACTED
TMPDIR=/var/folders/6v/n8nm5d6136b0br85j6llcy3c0000gn/T/
USER=REDACTED
XPC_SERVICE_NAME=0
LOGNAME=REDACTED
ITERM_SESSION_ID=REDACTED
__CF_USER_TEXT_ENCODING=0x0:0:0
SHLVL=1
OLDPWD=/Users/REDACTED/workspace/github_repos
ZSH=/Users/REDACTED/.oh-my-zsh
PAGER=less
LESS=-R
LSCOLORS=Gxfxcxdxbxegedabagacad
NVM_DIR=/Users/REDACTED/.nvm
NVM_CD_FLAGS=-q
NVM_BIN=/Users/REDACTED/.nvm/versions/node/v20.17.0/bin
NVM_INC=/Users/REDACTED/.nvm/versions/node/v20.17.0/include/node
LC_ALL=en_US.UTF-8
_=/usr/bin/env

➜  cpython git:(main) sw_vers
ProductName:		macOS
ProductVersion:		15.1.1
BuildVersion:		24B91

➜  cpython git:(main) gcc --version
Apple clang version 16.0.0 (clang-1600.0.26.6)
Target: x86_64-apple-darwin24.1.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

➜  cpython git:(main) xcodebuild -version
Xcode 16.2
Build version 16C5032a

➜  cpython git:(main) clang --version
Apple clang version 16.0.0 (clang-1600.0.26.6)
Target: x86_64-apple-darwin24.1.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

[erlend-aasland]

Still unable to reproduce. I'm on the same macOS version and the same compiler.

[srinivasreddy]

Here is the ./configure output i have captured.

config.log

[srinivasreddy]

Here is the make output i have capture with the command - make &> make.log. You should be able to see the warnings in the make.log file.

make.log

In file included from Python/ceval.c:904:
Python/generated_cases.c.h:808:31: warning: code will never be executed [-Wunreachable-code]
  808 |                 for (int _i = oparg; --_i >= 0;) {
      |                               ^~~~~
Python/generated_cases.c.h:694:31: warning: code will never be executed [-Wunreachable-code]
  694 |                 for (int _i = oparg*2; --_i >= 0;) {
      |                               ^~~~~
2 warnings generated.

Main branch at b4f799b

[picnixz]

Try to also do a make distclean, make clean and make cleantest. Some files might be left.