Don't define strlcpy on musl libc

[mstemm]

Falco has a build variant that uses musl libc, and musl libc already
defines strlcpy, so we don't want strlcpy when compiling with musl
libc.

Unfortunately, musl doesn't have a define like _MUSL_SOURCE that we
could use to detect when compiling with musl libc. So instead, use
MINIMAL_BUILD, which when set always means compiling with musl libc.

Signed-off-by: Mark Stemm mark.stemm@gmail.com

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/kind cleanup

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What this PR does / why we need it:

Which issue(s) this PR fixes:

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Does this PR introduce a user-facing change?:

Don't redefine strlcpy when using musl libc, which is true when building with MINIMAL_BUILD.

[LucaGuerra]

Thanks for this !
Now that I think about it, I believe MacOS, being based on BSD libraries, should have this defined too. Does MINIMAL_BUILD cover that case or should we add a define there?

[gnosek]

MINIMAL_BUILD is mostly orthogonal to the OS (we can and do have minimal Linux builds). I don't know if strlcpy comes with a matching #define so it will probably be easiest to #ifndef on some mac-specific macro.

[leogr]

Approved assuming this will make the Falco minimal build again. Anyway, I agree with @gnosek we shouldn't rely on MINIMAL_BUILD for that. Let me know if we find a better solution.

[poiana]

LGTM label has been added.

Git tree hash: 8b8b279f28c1fc4ea40e088de0336398c3e730e3

[mstemm]

Here's the declaration of strlcpy in musl's string.h, from http://git.musl-libc.org/cgit/musl/tree/include/string.h#n81:

#if defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
char *strsep(char **, const char *);
size_t strlcat (char *, const char *, size_t);
size_t strlcpy (char *, const char *, size_t);
void explicit_bzero (void *, size_t);
#endif

So musl declares it when either GNU_SOURCE or BSD_SOURCE are defined.

musl also doesn't have its own declaration like __MUSL_SOURCE, see https://wiki.musl-libc.org/faq.html.

So I'm not sure of any explicit define that we could use, other than something we could set when we set MINIMAL_BUILD, which is effectively this anyway.

[deepskyblue86]

I would rather do:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2b7544db..47c33719 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -69,3 +69,10 @@ if(CREATE_TEST_TARGETS AND NOT WIN32)
 			COMMAND ${CMAKE_MAKE_PROGRAM} run-unit-test-libsinsp
 		)
 endif()
+
+include(CheckSymbolExists)
+check_symbol_exists(strlcpy "string.h" HAVE_STRLCPY)
+if(HAVE_STRLCPY)
+	add_definitions(-DHAVE_STRLCPY)
+endif()
+
diff --git a/userspace/common/strlcpy.h b/userspace/common/strlcpy.h
index 7a9f4436..950099d4 100644
--- a/userspace/common/strlcpy.h
+++ b/userspace/common/strlcpy.h
@@ -14,10 +14,13 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+#pragma once
+
 #include <sys/types.h>
 #include <string.h>
 
 
+#ifndef HAVE_STRLCPY
 /*!
   \brief Copy up to size - 1 characters from the NUL-terminated string src to dst, NUL-terminating the result.
 
@@ -40,3 +43,6 @@ static inline size_t strlcpy(char *dst, const char *src, size_t size) {
 
     return srcsize;
 }
+
+#endif
+

No musl:

-- Looking for strlcpy
-- Looking for strlcpy - not found

With export CC="musl-gcc":

-- Looking for strlcpy
-- Looking for strlcpy - found

[mstemm]

I updated the PR to check for strlcpy at cmake time as @deepskyblue86 suggested, please take a look again?

[leogr]

LGTM

@deepskyblue86 Thank you for the suggestion!

[poiana]

LGTM label has been added.

Git tree hash: 06162cd850aac5d200d18f1d3e13e02fd0638b30

[gnosek]

/approve

[poiana]

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