Re: [gentoo-dev] [PATCH 1/5] toolchain-funcs.eclass: Add functions for detection of PIE / SSP in way compatible with GCC >=6.

[Michał Górny]

On śro, 2017-06-14 at 18:15 -0500, Matthias Maier wrote:
> From: Arfrever Frehtes Taifersar Arahesis <Arfrever@××××××.Org>
>
> Newly added tc-enables-pie(), tc-enables-ssp(), tc-enables-ssp-strong()
> and tc-enables-ssp-all() check macros instead of specs.
> This solution also works with older GCC and with Clang.
>
> Signed-off-by: Matthias Maier <tamiko@g.o>
> ---
>  eclass/toolchain-funcs.eclass | 71 +++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 71 insertions(+)
>
> diff --git a/eclass/toolchain-funcs.eclass b/eclass/toolchain-funcs.eclass
> index a0c359a950..3658c40518 100644
> --- a/eclass/toolchain-funcs.eclass
> +++ b/eclass/toolchain-funcs.eclass
> @@ -792,6 +792,77 @@ gcc-specs-stack-check() {
>  }
>
>
> +# @FUNCTION: tc-enables-pie
> +# @RETURN: Truth if the current compiler generates position-independent code (PIC) which can be linked into executables
> +# @DESCRIPTION:
> +# Return truth if the current compiler generates position-independent code (PIC)
> +# which can be linked into executables.
> +tc-enables-pie() {
> +	$($(tc-getCC) ${CPPFLAGS} ${CFLAGS} -E -P - <<-EOF 2> /dev/null
> +		#if defined(__PIE__)
> +		true
> +		#else
> +		false
> +		#endif
> +		EOF
> +	)

Looks quite horrible. Why can't you just compare the output against
a value instead of randomly executing it?

> +}
> +
> +# @FUNCTION: tc-enables-ssp
> +# @RETURN: Truth if the current compiler enables stack smashing protection (SSP) on at least minimal level
> +# @DESCRIPTION:
> +# Return truth if the current compiler enables stack smashing protection (SSP)
> +# on level corresponding to any of the following options:
> +#  -fstack-protector
> +#  -fstack-protector-strong
> +#  -fstack-protector-all
> +tc-enables-ssp() {
> +	$($(tc-getCC) ${CPPFLAGS} ${CFLAGS} -E -P - <<-EOF 2> /dev/null
> +		#if defined(__SSP__) || defined(__SSP_STRONG__) || defined(__SSP_ALL__)
> +		true
> +		#else
> +		false
> +		#endif
> +		EOF
> +	)
> +}
> +
> +# @FUNCTION: tc-enables-ssp-strong
> +# @RETURN: Truth if the current compiler enables stack smashing protection (SSP) on at least middle level
> +# @DESCRIPTION:
> +# Return truth if the current compiler enables stack smashing protection (SSP)
> +# on level corresponding to any of the following options:
> +#  -fstack-protector-strong
> +#  -fstack-protector-all
> +tc-enables-ssp-strong() {
> +	$($(tc-getCC) ${CPPFLAGS} ${CFLAGS} -E -P - <<-EOF 2> /dev/null
> +		#if defined(__SSP_STRONG__) || defined(__SSP_ALL__)
> +		true
> +		#else
> +		false
> +		#endif
> +		EOF
> +	)
> +}
> +
> +# @FUNCTION: tc-enables-ssp-all
> +# @RETURN: Truth if the current compiler enables stack smashing protection (SSP) on maximal level
> +# @DESCRIPTION:
> +# Return truth if the current compiler enables stack smashing protection (SSP)
> +# on level corresponding to any of the following options:
> +#  -fstack-protector-all
> +tc-enables-ssp-all() {
> +	$($(tc-getCC) ${CPPFLAGS} ${CFLAGS} -E -P - <<-EOF 2> /dev/null
> +		#if defined(__SSP_ALL__)
> +		true
> +		#else
> +		false
> +		#endif
> +		EOF
> +	)
> +}
> +
> +
>  # @FUNCTION: gen_usr_ldscript
>  # @USAGE: [-a] <list of libs to create linker scripts for>
>  # @DESCRIPTION:

-- 
Best regards,
Michał Górny