[PATCH]: 85582bbe4c configure: silent MacOS clang warning gnu-folding-constant

[<ge...@op...>]

This is an automated email from Gerrit.

"Antonio Borneo <bor...@gm...>" just uploaded a new patch set to Gerrit, which you can find at https://review.openocd.org/c/openocd/+/9431

-- gerrit

commit 85582bbe4c98b85a5f6f49d922b855ebafb0107f
Author: Antonio Borneo <bor...@gm...>
Date:   Mon Feb 2 14:52:45 2026 +0100

    configure: silent MacOS clang warning gnu-folding-constant
    
    On the specific fork of clang for MacOS, the compiler gets more
    strict on the use of GNU folding constants, generating warnings
    that halts the build of OpenOCD.
    The GNU folding constants are highlighted by upstream clang only
    for global variables. E.g.:
            const int len = 10;
            int array[len];
    generates the warning on:
            clang -c x.c
            x.c:2:5: warning: variable length array folded to constant
                     array as an extension [-Wgnu-folding-constant]
            int array[len];
                ^
    Apparently only the MacOS fork generates warning for folded
    constants inside a function. E.g.:
            int a(int *x);
            int b(void)
            {
                    const int len = 10;
                    int array[len];
                    return a*array);
            }
    does not return error even forcing -Wgnu-folding-constant on clang
    upstream.
    
    Current code triggers warning on the following lines due to the
    size of the array being computed from a const variable:
            jtag/drivers/xds110.c:354         unsigned char data[max_data + 1];
            flash/nor/dw-spi.c:950            uint8_t buffer[buffer_size];
            flash/nor/dw-spi.c:980            uint8_t buffer[buffer_size];
            flash/nor/dw-spi.c:1034           uint8_t buffer[buffer_size];
            flash/nor/dw-spi.c:1065           uint8_t buffer[buffer_size];
            flash/nor/jtagspi.c:364           uint8_t ..., write_buffer[max], ...;
            flash/nor/stmqspi.c:778           char ..., output[(2 + max + 256) * 3 + 8];
            flash/nor/xcf.c:392               uint8_t reference[L];
            target/target.c:3303              char output[line_bytecnt * 4 + 1];
            target/semihosting_common.c:1787  char buf[buf_len];
            target/smp.c:59                   char hex_buffer[len * 2 + 1];
            target/smp.c:60                   uint8_t buffer[len];
            target/cortex_m.c:296             uint32_t r_vals[n_r32];
            target/cortex_m.c:297             uint32_t dhcsr[n_r32];
            target/x86_32_common.c:1337       char output[line_bytecnt * 4 + 1];
            target/riscv/riscv.c:2377         uint8_t buffer[length];
            target/xtensa/xtensa.c:536        uint8_t ops_padded[max_oplen];
    
    While some of the const variable above could be replaced by macros,
    for the majority of them I don't see such need, and the use of
    const looks to me correct.
    
    Silent the warning adding the clang flag -Wno-gnu-folding-constant.
    The flag is not recognized by GCC, but it's silently ignored.
    
    Change-Id: I1d452af115355bc4949b1616648fe6544cc48318
    Reported-by: Frank Zeyda <fra...@gm...>
    Signed-off-by: Antonio Borneo <bor...@gm...>

diff --git a/configure.ac b/configure.ac
index c452cf5d3d..5bb76fe004 100644
--- a/configure.ac
+++ b/configure.ac
@@ -763,6 +763,7 @@ AC_DEFINE([_GNU_SOURCE],[1],[Use GNU C library extensions (e.g. stdndup).])
 GCC_WARNINGS="-Wall -Wstrict-prototypes -Wformat-security -Wshadow"
 AS_IF([test "x${gcc_wextra}" = "xyes"], [
   GCC_WARNINGS="${GCC_WARNINGS} -Wextra -Wno-unused-parameter"
+  GCC_WARNINGS="${GCC_WARNINGS} -Wno-gnu-folding-constant"
   GCC_WARNINGS="${GCC_WARNINGS} -Wbad-function-cast"
   GCC_WARNINGS="${GCC_WARNINGS} -Wcast-align"
   GCC_WARNINGS="${GCC_WARNINGS} -Wredundant-decls"

--