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gh-112301: Enable compiler flags with low performance impact and no warnings #120975

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Jun 26, 2024
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gh-112301: Enable compiler flags with low performance impact and no warnings #120975

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98d9ea0
Enable subset of flags with low performance impact and no warnings
nohlson Jun 21, 2024
1e84a87
Remove redundant -fno-strict-overflow option from config
nohlson Jun 25, 2024
257e3d7
📜🤖 Added by blurb_it.
blurb-it[bot] Jun 25, 2024
154fa05
Include explicit compiler options in news
nohlson Jun 25, 2024
1917b93
Remove trailing whitespace in news
nohlson Jun 25, 2024
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164 changes: 164 additions & 0 deletions configure
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12 changes: 12 additions & 0 deletions configure.ac
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Original file line number Diff line number Diff line change
Expand Up @@ -2451,6 +2451,18 @@ AS_VAR_IF([with_strict_overflow], [yes],
[BASECFLAGS="$BASECFLAGS $STRICT_OVERFLOW_CFLAGS"],
[BASECFLAGS="$BASECFLAGS $NO_STRICT_OVERFLOW_CFLAGS"])


# Enable flags that warn and protect for potential security vulnerabilities.
# These flags should be enabled by default for all builds.
AX_CHECK_COMPILE_FLAG([-Wimplicit-fallthrough], [BASECFLAGS="$BASECFLAGS -Wimplicit-fallthrough"], [AC_MSG_WARN([-Wimplicit-fallthrough not supported])])
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AX_CHECK_COMPILE_FLAG([-fstack-protector-strong], [BASECFLAGS="$BASECFLAGS -fstack-protector-strong"], [AC_MSG_WARN([-fstack-protector-strong not supported])])
AX_CHECK_COMPILE_FLAG([-fno-strict-overflow], [BASECFLAGS="$BASECFLAGS -fno-strict-overflow"], [AC_MSG_WARN([-fno-strict-overflow not supported])])
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But -fno-strict-overflow is already handled right above, isn't it?

dnl Historically, some of our code assumed that signed integer overflow
dnl is defined behaviour via twos-complement.
dnl Set STRICT_OVERFLOW_CFLAGS and NO_STRICT_OVERFLOW_CFLAGS depending on compiler support.
dnl Pass the latter to modules that depend on such behaviour.
_SAVE_VAR([CFLAGS])
CFLAGS="-fstrict-overflow -fno-strict-overflow"
AC_CACHE_CHECK([if $CC supports -fstrict-overflow and -fno-strict-overflow],
               [ac_cv_cc_supports_fstrict_overflow],
  AC_COMPILE_IFELSE(
    [AC_LANG_PROGRAM([[]], [[]])],
    [ac_cv_cc_supports_fstrict_overflow=yes],
    [ac_cv_cc_supports_fstrict_overflow=no]
  )
)
_RESTORE_VAR([CFLAGS])

AS_VAR_IF([ac_cv_cc_supports_fstrict_overflow], [yes],
          [STRICT_OVERFLOW_CFLAGS="-fstrict-overflow"
           NO_STRICT_OVERFLOW_CFLAGS="-fno-strict-overflow"],
          [STRICT_OVERFLOW_CFLAGS=""
           NO_STRICT_OVERFLOW_CFLAGS=""])

AC_MSG_CHECKING([for --with-strict-overflow])
AC_ARG_WITH([strict-overflow],
  AS_HELP_STRING(
    [--with-strict-overflow],
    [if 'yes', add -fstrict-overflow to CFLAGS, else add -fno-strict-overflow (default is no)]
  ),
  [
    AS_VAR_IF(
      [ac_cv_cc_supports_fstrict_overflow], [no],
      [AC_MSG_WARN([--with-strict-overflow=yes requires a compiler that supports -fstrict-overflow])],
      []
    )
  ],
  [with_strict_overflow=no]
)
AC_MSG_RESULT([$with_strict_overflow])

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Yes that is true. I only checked that it was enabled when compiling and it looks like it is redundant. I have removed my addition

case $CC in
*gcc*)
# Add GCC-specific compiler flags
AX_CHECK_COMPILE_FLAG([-Wtrampolines], [BASECFLAGS="$BASECFLAGS -Wtrampolines"], [AC_MSG_WARN([-Wtrampolines not supported])])
esac

case $GCC in
yes)
CFLAGS_NODIST="$CFLAGS_NODIST -std=c11"
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