aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--Config.in27
-rw-r--r--docs/manual/ccache-support.txt20
-rw-r--r--package/gcc/gcc.mk4
-rw-r--r--toolchain/toolchain-wrapper.c11
-rw-r--r--toolchain/toolchain-wrapper.mk4
5 files changed, 65 insertions, 1 deletions
diff --git a/Config.in b/Config.in
index 74aeb465ee..d795361148 100644
--- a/Config.in
+++ b/Config.in
@@ -286,6 +286,33 @@ config BR2_CCACHE_INITIAL_SETUP
These initial settings are applied after ccache has been compiled.
+config BR2_CCACHE_USE_BASEDIR
+ bool "Use relative paths"
+ default y
+ help
+ Allow ccache to convert absolute paths within the output
+ directory into relative paths.
+
+ During the build, many -I include directives are given with
+ an absolute path. These absolute paths end up in the hashes
+ that are computed by ccache. Therefore, when you build from a
+ different directory, the hash will be different and the
+ cached object will not be used.
+
+ To improve cache performance, set this option to y. This
+ allows ccache to rewrite absolute paths within the output
+ directory into relative paths. Note that only paths within
+ the output directory will be rewritten; therefore, if you
+ change BR2_HOST_DIR to point outside the output directory and
+ subsequently move it to a different location, this will lead
+ to cache misses.
+
+ This option has as a result that the debug information in the
+ object files also has only relative paths. Therefore, make
+ sure you cd to the build directory before starting gdb. See
+ the section "COMPILING IN DIFFERENT DIRECTORIES" in the
+ ccache manual for more information.
+
endif
config BR2_DEPRECATED
diff --git a/docs/manual/ccache-support.txt b/docs/manual/ccache-support.txt
index 992471dbf7..f6746ad7d8 100644
--- a/docs/manual/ccache-support.txt
+++ b/docs/manual/ccache-support.txt
@@ -33,3 +33,23 @@ make CCACHE_OPTIONS="--max-size=5G" ccache-options
# zero statistics counters
make CCACHE_OPTIONS="--zero-stats" ccache-options
-----------------
+
++ccache+ makes a hash of the source files and of the compiler options.
+If a compiler option is different, the cached object file will not be
+used. Many compiler options, however, contain an absolute path to the
+staging directory. Because of this, building in a different output
+directory would lead to many cache misses.
+
+To avoid this issue, buildroot has the +Use relative paths+ option
+(+BR2_CCACHE_USE_BASEDIR+). This will rewrite all absolute paths that
+point inside the output directory into relative paths. Thus, changing
+the output directory no longer leads to cache misses.
+
+A disadvantage of the relative paths is that they also end up to be
+relative paths in the object file. Therefore, for example, the debugger
+will no longer find the file, unless you cd to the output directory
+first.
+
+See https://ccache.samba.org/manual.html#_compiling_in_different_directories[the
+ccache manual's section on "Compiling in different directories"] for
+more details about this rewriting of absolute paths.
diff --git a/package/gcc/gcc.mk b/package/gcc/gcc.mk
index 103cbe17b7..420c4e9b7c 100644
--- a/package/gcc/gcc.mk
+++ b/package/gcc/gcc.mk
@@ -256,8 +256,10 @@ HOST_GCC_COMMON_CCACHE_HASH_FILES += package/gcc/$(GCC_VERSION)/1000-powerpc-lin
endif
endif
+# _CONF_OPTS contains some references to the absolute path of $(HOST_DIR),
+# so substitute those away.
HOST_GCC_COMMON_TOOLCHAIN_WRAPPER_ARGS += -DBR_CCACHE_HASH=\"`\
- printf '%s' $($(PKG)_CONF_OPTS) $(GCC_VERSION) \
+ printf '%s' $(subst $(HOST_DIR),@HOST_DIR@,$($(PKG)_CONF_OPTS)) \
| sha256sum - $(HOST_GCC_COMMON_CCACHE_HASH_FILES) \
| cut -c -64 | tr -d '\n'`\"
endif # BR2_CCACHE
diff --git a/toolchain/toolchain-wrapper.c b/toolchain/toolchain-wrapper.c
index d52115f51a..11f93f0fd5 100644
--- a/toolchain/toolchain-wrapper.c
+++ b/toolchain/toolchain-wrapper.c
@@ -268,6 +268,10 @@ int main(int argc, char **argv)
fprintf(stderr, "%sCCACHE_COMPILERCHECK='string:" BR_CCACHE_HASH "'",
(debug == 2) ? "\n " : " ");
#endif
+#ifdef BR_CCACHE_BASEDIR
+ fprintf(stderr, "%sCCACHE_BASEDIR='" BR_CCACHE_BASEDIR "'",
+ (debug == 2) ? "\n " : " ");
+#endif
for (i = 0; exec_args[i]; i++)
fprintf(stderr, "%s'%s'",
(debug == 2) ? "\n " : " ", exec_args[i]);
@@ -282,6 +286,13 @@ int main(int argc, char **argv)
return 3;
}
#endif
+#ifdef BR_CCACHE_BASEDIR
+ /* Allow compilercheck to be overridden through the environment */
+ if (setenv("CCACHE_BASEDIR", BR_CCACHE_BASEDIR, 0)) {
+ perror(__FILE__ ": Failed to set CCACHE_BASEDIR");
+ return 3;
+ }
+#endif
if (execv(exec_args[0], exec_args))
perror(path);
diff --git a/toolchain/toolchain-wrapper.mk b/toolchain/toolchain-wrapper.mk
index 749afd7a59..c78363a2ed 100644
--- a/toolchain/toolchain-wrapper.mk
+++ b/toolchain/toolchain-wrapper.mk
@@ -20,6 +20,10 @@ ifeq ($(BR2_CCACHE),y)
TOOLCHAIN_WRAPPER_ARGS += -DBR_CCACHE
endif
+ifeq ($(BR2_CCACHE_USE_BASEDIR),y)
+TOOLCHAIN_WRAPPER_ARGS += -DBR_CCACHE_BASEDIR='"$(BASE_DIR)"'
+endif
+
# For simplicity, build directly into the install location
define TOOLCHAIN_BUILD_WRAPPER
$(Q)mkdir -p $(HOST_DIR)/usr/bin