2

I have this in my Make file..

# Create list of object files
#
LIB_OBJS =  -Wl,--start-group \
$(T_OBJ_DIR)/Source1.o \
$(T_OBJ_DIR)/Source2.o \
$(T_OBJ_DIR)/Source3.o \
$(T_OBJ_DIR)/Source4.o \
$(T_OBJ_DIR)/Source5.o \
-Wl,--end-group \

Could anyone please explain What "-Wl,--start-group" and "-Wl,--end-group" mean?

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  • They actually have no effect. The `--start-group` and `--end-group` options, as documented in Etan Reisner's answer, only works with archives (`.a` files, otherwise known as libraries). The option is unnecessary with object files (`.o`) as the linker will search through all object files in order to resolve undefined references. – Ross Ridge Jun 19 '15 at 06:52

1 Answers1

3

Those are flags to the linker (that's what -Wl means) so the documentation for ld (the linker) will explain the rest.

From the man page for GNU ld:

-( archives -)

--start-group archives --end-group

The archives should be a list of archive files. They may be either explicit file names, or -l options.

The specified archives are searched repeatedly until no new undefined references are created. Normally, an archive is searched only once in the order that it is specified on the command line. If a symbol in that archive is needed to resolve an undefined symbol referred to by an object in an archive that appears later on the command line, the linker would not be able to resolve that reference. By grouping the archives, they all be searched repeatedly until all possible references are resolved.

Using this option has a significant performance cost. It is best to use it only when there are unavoidable circular references between two or more archives.

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Etan Reisner
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