[OB PATCH] Fix build errors in with clang in gdb.compile/compile-cplus.c

[Pedro Alves]

On 5/29/20 5:43 PM, Gary Benson via Gdb-patches wrote:
> Clang fails to compile the file, with the following error:
>   fatal error: 'iostream' file not found
> 
> This prevents the following testcase from executing:
>   gdb.compile/compile-cplus.exp
> 
> The testcase sets additional_flags when building with GCC, which
> this commit causes to also be set when building with clang.  This
> makes the testcase fail to build with a different error:
>   warning: treating 'c' input as 'c++' when in C++ mode, this behavior
>   is deprecated [-Wdeprecated]
> so this commit adds -Wno-deprecated in two places to sidestep this.
> Note that, while allowing the testcase to build, this commit reveals
> failures when the testsuite is built using clang.
> 
> gdb/testsuite/ChangeLog:
> 
> 	* gdb.compile/compile-cplus.exp (additional_flags): Also
> 	set when building with clang.
> 	(additional_flags, srcfilesoptions): Pass -Wno-deprecated
> 	when building with clang.
> ---
>  gdb/testsuite/ChangeLog                     |  7 +++++++
>  gdb/testsuite/gdb.compile/compile-cplus.exp | 15 +++++++++++++--
>  2 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/gdb/testsuite/gdb.compile/compile-cplus.exp b/gdb/testsuite/gdb.compile/compile-cplus.exp
> index cca5b20..85b2f20 100644
> --- a/gdb/testsuite/gdb.compile/compile-cplus.exp
> +++ b/gdb/testsuite/gdb.compile/compile-cplus.exp
> @@ -19,11 +19,16 @@ standard_testfile .c compile-shlib.c compile-constvar.S compile-nodebug.c
>  
>  get_compiler_info
>  set options {}
> -if [test_compiler_info gcc*] {
> +if { [test_compiler_info gcc*] || [test_compiler_info clang*] } {
>      lappend options additional_flags=-g3
>      lappend options additional_flags=-std=gnu++11
>      lappend options c++
>  }
> +if [test_compiler_info clang*] {
> +    # Treating C input as C++ is deprecated in Clang, so
> +    # the build will fail without disabling -Wdeprecated.
> +    lappend options additional_flags=-Wno-deprecated
> +}

I think

 lappend options "additional_flags=-x c++"

in the previous "if" would be better.  Even better would be to tweak
gdb_compile or thereabouts to make the "c++" option automatically add
"-x c++" to the compiler options with clang.  That would handle
everywhere this could be an issue all at once.  WDYT?

BTW, it looks like a bug that appending the "c++" option is inside
the if, rather than outside.

Thanks,
Pedro Alves

>  
>  if { ![istarget x86_64-*-* ] || ![is_lp64_target] } {
>      verbose "Skipping x86_64 LOC_CONST test."
> @@ -34,7 +39,13 @@ set srcfilesoptions [list ${srcfile} ${options}]
>  if { $srcfile3 != "" } {
>      lappend srcfilesoptions $srcfile3 ${options}
>  }
> -lappend srcfilesoptions $srcfile4 "nodebug c++"
> +set srcfile4options "nodebug c++"
> +if [test_compiler_info clang*] {
> +    # Treating C input as C++ is deprecated in Clang, so
> +    # the build will fail without disabling -Wdeprecated.
> +    set srcfile4options "$srcfile4options additional_flags=-Wno-deprecated"
> +}
> +lappend srcfilesoptions $srcfile4 $srcfile4options
>  if { [eval build_executable_from_specs ${testfile}.exp $testfile {$options} ${srcfilesoptions}] } {
>      return -1
>  }
>