[PATCH 3/5] gcc: Add --nostdlib++ option

[Richard Purdie]

OpenEmbedded/Yocto Project builds libgcc and the other gcc runtime libraries
separately from the compiler and slightly differently to the standard gcc build.

In general this works well but in trying to build them separately we run into
an issue since we're using our gcc, not xgcc and there is no way to tell configure
to use libgcc but not look for libstdc++.

This adds such an option allowing such configurations to work.

2021-10-26 Richard Purdie <richard.purdie@linuxfoundation.org>

gcc/c-family/ChangeLog:

    * c.opt: Add --nostdlib++ option

gcc/cp/ChangeLog:

    * g++spec.c (lang_specific_driver): Add --nostdlib++ option

gcc/ChangeLog:

    * doc/invoke.texi: Document --nostdlib++ option
    * gcc.c: Add --nostdlib++ option

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
---
 gcc/c-family/c.opt  | 4 ++++
 gcc/cp/g++spec.c    | 1 +
 gcc/doc/invoke.texi | 8 +++++++-
 gcc/gcc.c           | 1 +
 4 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 06457ac739e..ee742c831fd 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -2190,6 +2190,10 @@ nostdinc++
 C++ ObjC++
 Do not search standard system include directories for C++.
 
+nostdlib++
+Driver
+Do not link standard C++ runtime library
+
 o
 C ObjC C++ ObjC++ Joined Separate
 ; Documented in common.opt
diff --git a/gcc/cp/g++spec.c b/gcc/cp/g++spec.c
index 3c9bd1490b4..818beb61cee 100644
--- a/gcc/cp/g++spec.c
+++ b/gcc/cp/g++spec.c
@@ -159,6 +159,7 @@ lang_specific_driver (struct cl_decoded_option **in_decoded_options,
       switch (decoded_options[i].opt_index)
 	{
 	case OPT_nostdlib:
+	case OPT_nostdlib__:
 	case OPT_nodefaultlibs:
 	  library = -1;
 	  break;
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 71992b8c597..d89b08b3080 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -239,6 +239,7 @@ in the following sections.
 -fno-weak  -nostdinc++ @gol
 -fvisibility-inlines-hidden @gol
 -fvisibility-ms-compat @gol
+-nostdlib++ @gol
 -fext-numeric-literals @gol
 -flang-info-include-translate@r{[}=@var{header}@r{]} @gol
 -flang-info-include-translate-not @gol
@@ -638,7 +639,7 @@ Objective-C and Objective-C++ Dialects}.
 -pie  -pthread  -r  -rdynamic @gol
 -s  -static  -static-pie  -static-libgcc  -static-libstdc++ @gol
 -static-libasan  -static-libtsan  -static-liblsan  -static-libubsan @gol
--shared  -shared-libgcc  -symbolic @gol
+-shared  -shared-libgcc  -symbolic -nostdlib++ @gol
 -T @var{script}  -Wl,@var{option}  -Xlinker @var{option} @gol
 -u @var{symbol}  -z @var{keyword}}
 
@@ -16134,6 +16135,11 @@ Specify that the program entry point is @var{entry}.  The argument is
 interpreted by the linker; the GNU linker accepts either a symbol name
 or an address.
 
+@item -nostdlib++
+@opindex nostdlib++
+Do not use the standard system C++ runtime libraries when linking.
+Only the libraries you specify will be passed to the linker.
+
 @item -pie
 @opindex pie
 Produce a dynamically linked position independent executable on targets
diff --git a/gcc/gcc.c b/gcc/gcc.c
index 506c2acc282..abb900a4247 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -1167,6 +1167,7 @@ proper position among the other output files.  */
     %(mflib) " STACK_SPLIT_SPEC "\
     %{fprofile-arcs|fprofile-generate*|coverage:-lgcov} " SANITIZER_SPEC " \
     %{!nostdlib:%{!r:%{!nodefaultlibs:%(link_ssp) %(link_gcc_c_sequence)}}}\
+    %{!nostdlib++:}\
     %{!nostdlib:%{!r:%{!nostartfiles:%E}}} %{T*}  \n%(post_link) }}}}}}"
 #endif
 
-- 
2.25.1