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curl using cmake on arm32 systems build error -Werror=cast-align #13035

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curl using cmake on arm32 systems build error -Werror=cast-align#13035
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@heitbaum
heitbaum
opened on Mar 3, 2024

I did this

build curl using cmake on arm32 systems errors due to http_chunks.c:399:32: error: cast increases required alignment of target type [-Werror=cast-align]. Build on aarch64 and x86_64 build correctly

BUILD      curl (target)
    TOOLCHAIN      cmake (auto-detect)
Executing (target): cmake -GNinja -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DCMAKE_TOOLCHAIN_FILE=/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/toolchain/etc/cmake-armv7ve-libreelec-linux-gnueabihf.conf -DCMAKE_INSTALL_PREFIX=/usr -DCMAKE_BUILD_TYPE=MinSizeRel -DENABLE_DEBUG=OFF -DCURL_LTO=ON -DCURL_WERROR=ON -DENABLE_CURLDEBUG=OFF -DENABLE_ARES=OFF -DCURL_DISABLE_HTTP=OFF -DCURL_DISABLE_FTP=OFF -DCURL_DISABLE_FILE=OFF -DCURL_DISABLE_LDAP=ON -DCURL_DISABLE_LDAPS=ON -DCURL_DISABLE_RTSP=OFF -DCURL_DISABLE_PROXY=OFF -DCURL_DISABLE_DICT=ON -DCURL_DISABLE_TELNET=ON -DCURL_DISABLE_TFTP=ON -DCURL_DISABLE_POP3=ON -DCURL_DISABLE_IMAP=ON -DCURL_DISABLE_SMB=ON -DCURL_DISABLE_SMTP=ON -DCURL_DISABLE_GOPHER=ON -DCURL_DISABLE_MQTT=ON -DENABLE_MANUAL=OFF -DENABLE_IPV6=ON -DENABLE_THREADED_RESOLVER=ON -DCURL_DISABLE_VERBOSE_STRINGS=OFF -DCURL_WINDOWS_SSPI=OFF -DCURL_DISABLE_COOKIES=OFF -DCURL_HIDDEN_SYMBOLS=ON -DCURL_USE_GSSAPI=OFF -DUSE_ZLIB=ON -DCURL_BROTLI=OFF -DCURL_ZSTD=OFF -DRANDOM_FILE=/dev/urandom -DCURL_USE_GNUTLS=OFF -DCURL_ENABLE_SSL=ON -DCURL_USE_MBEDTLS=OFF -DCURL_CA_BUNDLE=/run/libreelec/cacert.pem -DCURL_CA_PATH=none -DCURL_USE_LIBPSL=OFF -DCURL_USE_LIBSSH2=OFF -DUSE_LIBRTMP=ON -DUSE_LIBIDN2=ON -DUSE_NGHTTP2=ON /var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0
-- Using CMake version 3.28.3
-- curl version=[8.6.0]
-- Picky compiler options: -pedantic-errors -W -Wall -pedantic -Wbad-function-cast -Wconversion -Winline -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wno-long-long -Wno-multichar -Wpointer-arith -Wshadow -Wsign-compare -Wundef -Wunused -Wwrite-strings -Waddress -Wattributes -Wcast-align -Wdeclaration-after-statement -Wdiv-by-zero -Wempty-body -Wendif-labels -Wfloat-equal -Wformat-security -Wignored-qualifiers -Wmissing-field-initializers -Wmissing-noreturn -Wno-format-nonliteral -Wno-system-headers -Wold-style-definition -Wredundant-decls -Wsign-conversion -Wno-error=sign-conversion -Wstrict-prototypes -Wtype-limits -Wunreachable-code -Wunused-parameter -Wvla -Wclobbered -Wmissing-parameter-type -Wold-style-declaration -Wstrict-aliasing=3 -Wtrampolines -Wformat=2 -Warray-bounds=2 -ftree-vrp -Wduplicated-cond -Wnull-dereference -fdelete-null-pointer-checks -Wshift-negative-value -Wshift-overflow=2 -Walloc-zero -Wduplicated-branches -Wformat-overflow=2 -Wformat-truncation=2 -Wimplicit-fallthrough -Wrestrict -Warith-conversion -Wdouble-promotion -Wenum-conversion -Wpragmas -Wunused-const-variable
CMake Warning at CMake/Macros.cmake:96 (message):
  Found no *nroff program
Call Stack (most recent call first):
  CMakeLists.txt:315 (curl_nroff_check)


CMake Warning at CMakeLists.txt:321 (message):
  Perl not found, or nroff not useful.  Will not build manuals.


-- LTO supported and enabled
-- Enabled features: SSL IPv6 UnixSockets libz AsynchDNS IDN Largefile alt-svc HSTS NTLM TLS-SRP HTTP2 HTTPS-proxy threadsafe
-- Enabled protocols: FILE FTP FTPS HTTP HTTPS IPFS IPNS RTMP RTSP
-- Enabled SSL backends: OpenSSL
-- Configuring done (0.1s)
-- Generating done (0.2s)
-- Build files have been written to: /var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/.armv7ve-libreelec-linux-gnueabihf
Executing (target): ninja 
[25/80] Building C object lib/CMakeFiles/libcurl_shared.dir/http_chunks.c.o
FAILED: lib/CMakeFiles/libcurl_shared.dir/http_chunks.c.o 
/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/toolchain/bin/armv7ve-libreelec-linux-gnueabihf-gcc -DBUILDING_LIBCURL -DCURL_HIDDEN_SYMBOLS -DHAVE_CONFIG_H -Dlibcurl_shared_EXPORTS -I/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/include -I/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/.armv7ve-libreelec-linux-gnueabihf/lib/../include -I/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/lib/.. -I/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/lib/../include -I/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/.armv7ve-libreelec-linux-gnueabihf/lib/.. -I/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/lib -I/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/.armv7ve-libreelec-linux-gnueabihf/lib -march=armv7ve -mtune=cortex-a7 -mabi=aapcs-linux -Wno-psabi -Wa,-mno-warn-deprecated -mfloat-abi=hard -mfpu=neon-vfpv4 -Wall -pipe  -O2 -fomit-frame-pointer -DNDEBUG  -pedantic-errors -W -Wall -pedantic -Wbad-function-cast -Wconversion -Winline -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wno-long-long -Wno-multichar -Wpointer-arith -Wshadow -Wsign-compare -Wundef -Wunused -Wwrite-strings -Waddress -Wattributes -Wcast-align -Wdeclaration-after-statement -Wdiv-by-zero -Wempty-body -Wendif-labels -Wfloat-equal -Wformat-security -Wignored-qualifiers -Wmissing-field-initializers -Wmissing-noreturn -Wno-format-nonliteral -Wno-system-headers -Wold-style-definition -Wredundant-decls -Wsign-conversion -Wno-error=sign-conversion -Wstrict-prototypes -Wtype-limits -Wunreachable-code -Wunused-parameter -Wvla -Wclobbered -Wmissing-parameter-type -Wold-style-declaration -Wstrict-aliasing=3 -Wtrampolines -Wformat=2 -Warray-bounds=2 -ftree-vrp -Wduplicated-cond -Wnull-dereference -fdelete-null-pointer-checks -Wshift-negative-value -Wshift-overflow=2 -Walloc-zero -Wduplicated-branches -Wformat-overflow=2 -Wformat-truncation=2 -Wimplicit-fallthrough -Wrestrict -Warith-conversion -Wdouble-promotion -Wenum-conversion -Wpragmas -Wunused-const-variable -Werror -DDUMMYOPT -fPIC -fvisibility=hidden -MD -MT lib/CMakeFiles/libcurl_shared.dir/http_chunks.c.o -MF lib/CMakeFiles/libcurl_shared.dir/http_chunks.c.o.d -o lib/CMakeFiles/libcurl_shared.dir/http_chunks.c.o -c /var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/lib/http_chunks.c
/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/lib/http_chunks.c: In function 'cw_chunked_init':
/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/lib/http_chunks.c:389:32: error: cast increases required alignment of target type [-Werror=cast-align]
  389 |   struct chunked_writer *ctx = (struct chunked_writer *)writer;
      |                                ^
/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/lib/http_chunks.c: In function 'cw_chunked_close':
/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/lib/http_chunks.c:399:32: error: cast increases required alignment of target type [-Werror=cast-align]
  399 |   struct chunked_writer *ctx = (struct chunked_writer *)writer;
      |                                ^
/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/lib/http_chunks.c: In function 'cw_chunked_write':
/var/media/DATA/home-rudi/LibreELEC.kernel11/build.LibreELEC-RPi2.arm-12.0-devel/build/curl-8.6.0/lib/http_chunks.c:407:32: error: cast increases required alignment of target type [-Werror=cast-align]
  407 |   struct chunked_writer *ctx = (struct chunked_writer *)writer;
      |                                ^
cc1: all warnings being treated as errors
[40/80] Building C object lib/CMakeFiles/libcurl_shared.dir/vtls/openssl.c.o
ninja: build stopped: subcommand failed.

I expected the following

Successful compile

curl/libcurl version

curl 8.6.0

operating system

LibreELEC HEAD

Activity

  1. bagder
    added
    build
    on Mar 3, 2024

  2. icing commented on Mar 4, 2024

    @icing
    icing
    on Mar 4, 2024
    Contributor

    This looks like a wrong compiler warning. struct Curl_cwriter is the first member of struct chunked_writer. Afaik, this is legal C.

  3. heitbaum commented on Mar 4, 2024

    @heitbaum
    heitbaum
    on Mar 4, 2024
    Author

    fyi - it is gcc version 13.2.0 (GCC)

  4. icing commented on Mar 4, 2024

    @icing
    icing
    on Mar 4, 2024
    Contributor

    Hmm, is this the only file where you get those errors? We use the same casting in content_encding.c for some time.

  5. heitbaum commented on Mar 4, 2024

    @heitbaum
    heitbaum
    on Mar 4, 2024
    Author

    I just tested with CFLAGS+=" -Wno-error=cast-align" and it is only those 3 lines that error/warn. And the errors only happen on the arm32 bit build. The aarch64 and x86_64 builds are clean with no errors.

  6. bagder commented on Mar 4, 2024

    @bagder
    bagder
    on Mar 4, 2024
    Member

    Does this patch silence the warnings? (against current master, might not work cleanly on 8.6.0)

    diff --git a/lib/http_chunks.c b/lib/http_chunks.c
index 3236c0e47..c1f5e42f5 100644
--- a/lib/http_chunks.c
+++ b/lib/http_chunks.c
@@ -389,10 +389,21 @@ CURLcode Curl_httpchunk_read(struct Curl_easy *data,
 struct chunked_writer {
   struct Curl_cwriter super;
   struct Curl_chunker ch;
 };
 
+#if defined(__GNUC__)
+/* Ignore cast-align warnings (on 32 bit arm):
+
+   error: cast increases required alignment of target type [-Werror=cast-align]
+        |   struct chunked_writer *ctx = (struct chunked_writer *)writer;
+                                         ^
+ */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wcast-align"
+#endif
+
 static CURLcode cw_chunked_init(struct Curl_easy *data,
                                 struct Curl_cwriter *writer)
 {
   struct chunked_writer *ctx = (struct chunked_writer *)writer;
 
@@ -411,10 +422,14 @@ static void cw_chunked_close(struct Curl_easy *data,
 static CURLcode cw_chunked_write(struct Curl_easy *data,
                                  struct Curl_cwriter *writer, int type,
                                  const char *buf, size_t blen)
 {
   struct chunked_writer *ctx = (struct chunked_writer *)writer;
+#if defined(__GNUC__)
+/* Stop ignoring cast-align warnings */
+#pragma GCC diagnostic pop
+#endif
   CURLcode result;
   size_t consumed;
 
   if(!(type & CLIENTWRITE_BODY))
     return Curl_cwriter_write(data, writer->next, type, buf, blen);

  7. icing commented on Mar 4, 2024

    @icing
    icing
    on Mar 4, 2024
    Contributor

    We could reorder the struct to move the char *'s to later, should that help. But I am unable to verify this.

    @heitbaum could you test if it helps to reshuffle the members in struct Curl_cwriter?

  8. heitbaum commented on Mar 4, 2024

    @heitbaum
    heitbaum
    on Mar 4, 2024
    Author

    Does this patch silence the warnings? (against current master, might not work cleanly on 8.6.0)

    I have run a full build on all of our targets. This addresses the issue. No warnings or errors - 👍.

  9. heitbaum commented on Mar 4, 2024

    @heitbaum
    heitbaum
    on Mar 4, 2024
    Author

    We could reorder the struct to move the char *'s to later, should that help. But I am unable to verify this.

    @heitbaum could you test if it helps to reshuffle the members in struct Curl_cwriter?

    I’ll try.

  10. heitbaum commented on Mar 4, 2024

    @heitbaum
    heitbaum
    on Mar 4, 2024
    Author

    I’ve had a look, and don’t think it is the struct itself? I tried with char align[] with no success.. Might be wrong. Is it the pointer? The pointer is 4 bytes on arm32 and 8 on aarch64/x86_64.

    Curl_cwriter is 12 bytes on arm32 and 24 or x86_64
    chunked_writer would be 12+(16+28) or 24+(28+36) I think..
    I’m not sure I understand fully the passing in the pointer to Curl_cwriter and casting it to the chunked_writer pointer.

    im a bit confused now.

  11. icing commented on Mar 4, 2024

    @icing
    icing
    on Mar 4, 2024
    Contributor

    Same here. Do not really understand it. Let's go with @bagder 's proposal.

  12. bagder commented on Mar 4, 2024

    @bagder
    bagder
    on Mar 4, 2024
    Member

    I'll turn it into a PR in a sec

  13. bagder
    added a commit that references this issue on Mar 5, 2024

    http_chunks: disable a cast-align gcc warning on 32 bit arm

    08fb31d

  14. bagder commented on Mar 5, 2024

    @bagder
    bagder
    on Mar 5, 2024
    Member

    the "sec" became 17 hours 😁

  15. icing commented on Mar 5, 2024

    @icing
    icing
    on Mar 5, 2024
    Contributor

    You are just accelerating too fast now and then, time dilation sets in.

  16. vszakats commented on Mar 5, 2024

    @vszakats
    vszakats
    on Mar 5, 2024
    Member

    This isn't limited to gcc or arm32. llvm/clang 17.0.6 also complains, e.g. in this case for Windows x64 x86:

    ./lib/sendf.c:490:27: warning: cast from 'struct Curl_creader *' to 'struct cr_in_ctx *' increases required alignment from 4 to 8 [-Wcast-align]
  490 |   struct cr_in_ctx *ctx = (struct cr_in_ctx *)reader;
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~
./lib/sendf.c:503:27: warning: cast from 'struct Curl_creader *' to 'struct cr_in_ctx *' increases required alignment from 4 to 8 [-Wcast-align]
  503 |   struct cr_in_ctx *ctx = (struct cr_in_ctx *)reader;
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~
./lib/sendf.c:594:27: warning: cast from 'struct Curl_creader *' to 'struct cr_in_ctx *' increases required alignment from 4 to 8 [-Wcast-align]
  594 |   struct cr_in_ctx *ctx = (struct cr_in_ctx *)reader;
      |                           ^~~~~~~~~~~~~~~~~~~~~~~~~~    
./lib/sendf.c:790:29: warning: cast from 'struct Curl_creader *' to 'struct cr_in_ctx *' increases required alignment from 4 to 8 [-Wcast-align]
  790 |     struct cr_in_ctx *ctx = (struct cr_in_ctx *)r;      
      |                             ^~~~~~~~~~~~~~~~~~~~~       
4 warnings generated.

    edit: this is different code, but the same pattern with a reader (instead of writer), and the same warning.

  17. icing commented on Mar 5, 2024

    @icing
    icing
    on Mar 5, 2024
    Contributor

    Ok, it's time to rethink this way of casting. We started this in content_encoding.c ages ago, but modern compilers and arch do not seem to like that.

    I will make a PR to change that, given struct Curl_cwriter and struct Curl_creader a member void *ctx, similar to what we use in connection filters.

    @bagder any intent to merge #13026 and #13039 soon? I'd like to do the rework on top of that to avoid rebasing.

  18. bagder commented on Mar 5, 2024

    @bagder
    bagder
    on Mar 5, 2024
    Member

    I'll have them merged before EOD!

  19. icing commented on Mar 5, 2024

    @icing
    icing
    on Mar 5, 2024
    Contributor

    Thanks. Then I'll start that change tomorrow.

  20. icing commented on Mar 5, 2024

    @icing
    icing
    on Mar 5, 2024
    Contributor

    My current explanation for this mess: https://chaos.social/@icing/112043038186968686

  21. icing
    added a commit that references this issue on Mar 6, 2024

    client reader/writer, ctx casting

    73db51c

  22. icing commented on Mar 6, 2024

    @icing
    icing
    on Mar 6, 2024
    Contributor

    Could you verify that #13059 fixes the issue in your builds? Thanks!

  23. heitbaum commented on Mar 6, 2024

    @heitbaum
    heitbaum
    on Mar 6, 2024
    Author

    Could you verify that #13059 fixes the issue in your builds? Thanks!

    Just tested master db5c9f4 with #13059 and #12930 - all built successfully across arm32, aarch64, x86_64

  24. vszakats commented on Mar 6, 2024

    @vszakats
    vszakats
    on Mar 6, 2024
    Member

    #13059 fixed my build case. (it wasn't x64, but x86, just noticed it now, but Windows and llvm/clang 17 it is)

  25. bagder
    closed this as completedin 9978d40on Mar 6, 2024
  26. clayne
    added a commit that references this issue on Mar 6, 2024

    lib: add `void *ctx` to reader/writer instances

    9978d40
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