[Bug libbacktrace/103822] New: libbacktrace make check fails with GNU Make 3.81

[fxcoudert at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103822

            Bug ID: 103822
           Summary: libbacktrace make check fails with GNU Make 3.81
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libbacktrace
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fxcoudert at gcc dot gnu.org
                CC: ian at gcc dot gnu.org
  Target Milestone: ---

The failure is observed on macOS (*-apple-darwin21), where the system make is
GNU Make 3.81. But I think it would occur on all platforms that are not ELF and
use GNU Make 3.81. Running `make check` leads to this failure:

elf_32.c:144:26: error: extra tokens at end of #undef directive [-Werror]
  144 | #undef BACKTRACE_ELF_SIZE#define BACKTRACE_ELF_SIZE 32
      |                          ^

where the invalid elf_32.c is generated by this command:

SEARCH='#error "Unknown BACKTRACE_ELF_SIZE"'; \
        REPLACE='#undef BACKTRACE_ELF_SIZE\
        #define BACKTRACE_ELF_SIZE'; \
        /usr/bin/sed "s/^$SEARCH\$/$REPLACE 32/" \
                /tmp/gcc-darwin-arm64/libbacktrace/elf.c \
                > elf_32.c.tmp
mv elf_32.c.tmp elf_32.c


This tries to have a newline inside the REPLACE string, and pass it to sed.
This fails with GNU Make < 4. And GCC requires "GNU make version 3.80 (or
later)".

The portable solution is given in the autoconf manual:
https://www.gnu.org/software/autoconf/manual/autoconf-2.69/html_node/Newlines-in-Make-Rules.html

The patch to fix it is this:

diff --git a/libbacktrace/Makefile.am b/libbacktrace/Makefile.am
index 8874f41338a..180a3b1a809 100644
--- a/libbacktrace/Makefile.am
+++ b/libbacktrace/Makefile.am
@@ -145,18 +145,18 @@ endif HAVE_OBJCOPY_DEBUGLINK
 endif HAVE_ELF

 elf_%.c: elf.c
+       nlinit=`echo 'nl="'; echo '"'`; eval "$$nlinit"; \
        SEARCH='#error "Unknown BACKTRACE_ELF_SIZE"'; \
-       REPLACE='#undef BACKTRACE_ELF_SIZE\
-       #define BACKTRACE_ELF_SIZE'; \
+       REPLACE='#undef BACKTRACE_ELF_SIZE\\$${nl}#define BACKTRACE_ELF_SIZE';
\
        $(SED) "s/^$$SEARCH\$$/$$REPLACE $*/" \
                $< \
                > $@.tmp
        mv $@.tmp $@

 xcoff_%.c: xcoff.c
+       nlinit=`echo 'nl="'; echo '"'`; eval "$$nlinit"; \
        SEARCH='#error "Unknown BACKTRACE_XCOFF_SIZE"'; \
-       REPLACE='#undef BACKTRACE_XCOFF_SIZE\
-       #define BACKTRACE_XCOFF_SIZE'; \
+       REPLACE='#undef BACKTRACE_XCOFF_SIZE\\$${nl}#define
BACKTRACE_XCOFF_SIZE'; \
        $(SED) "s/^$$SEARCH\$$/$$REPLACE $*/" \
                $< \
                > $@.tmp