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Fix compilation of .c files as C++ when using Clang

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In commit 221db974e6, this patch:

    2020-06-24  Pedro Alves  <palves@redhat.com>

    * lib/gdb.exp (gdb_compile): Pass "-x c++" explicitly when
    compiling C++ programs.

attempted to fix problems with testcases that compile .c files
with the C++ compiler.  They pass the "c++" option to gdb_compile,
resulting in the following error when using Clang:

    gdb compile failed, clang-10: warning: treating 'c' input as 'c++'
    when in C++ mode, this behavior is deprecated [-Wdeprecated]

This fix did not work for gdb.base/infcall-nested-structs-c++.exp,
however: the "-x c++" appeared in the compiler's commandline after
the .c file, so the option was not enabled for that file.

The previous files fixed all used build_executable_from_specs, which
compiles and links in separate steps, using gdb_compile: the compile
step passes $type=object to gdb_compile, while the link step passes
$type=executable.

gdb.base/infcall-nested-structs-c++.exp uses gdb_compile directly
instead, and it passes $type=executable to compile and link all in
one step.  Pedro found that DejaGnu's default_target_compile adds
the sources at the end when $type=object, but at the beginning when
$type=executable:

    # This is obscure: we put SOURCES at the end when building an
    # object, because otherwise, in some situations, libtool will
    # become confused about the name of the actual source file.
    if {$type == "object"} {
        set opts "$add_flags $sources"
    } else {
        set opts "$sources $add_flags"
    }

This commit moves the "-x c++" earlier in the compiler's commandline.
Unfortunately this then broke the testcase that required the original
fix, gdb.compile/compile-cplus.exp: the "-x c++" was being parsed for
the linker pass, causing the compiler to attempt to parse the .o files
as C++.  This commit makes passing "-x c++" conditional on the source
being a .c file.

gdb/testsuite/ChangeLog:

	* lib/gdb.exp (gdb_compile): Pass "-x c++" earlier, and only
	for .c files.
This commit is contained in:
Gary Benson 2020-09-25 14:29:35 +01:00
parent 5a805384b8
commit 68d654afdf
2 changed files with 8 additions and 2 deletions
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5
gdb/testsuite/ChangeLog
View file

@ -1,3 +1,8 @@
2020-09-25 Gary Benson <gbenson@redhat.com>
* lib/gdb.exp (gdb_compile): Pass "-x c++" earlier, and only
for .c files.
2020-09-24 Tom Tromey <tromey@adacore.com>
PR tui/26638:

5
gdb/testsuite/lib/gdb.exp
View file

@ -3944,8 +3944,9 @@ proc gdb_compile {source dest type options} {
# explicitly force C++ language.
if { [lsearch -exact $options getting_compiler_info] == -1
&& [lsearch -exact $options c++] != -1
&& [test_compiler_info "clang-*"]} {
lappend new_options additional_flags=-x\ c++
&& [string match *.c $source] != 0
&& [test_compiler_info "clang-*"] } {
lappend new_options early_flags=-x\ c++
}
# Place (and look for) Fortran `.mod` files in the output