protobuf: conflict with abseil-cpp@20250512: for @26:29

[zackgalbreath]

The absl::if_constexpr target was removed in the 20250512 release of abseil-cpp. protobuf attempts to link to it in versions 26:29

[bernhardkaindl]

@zackgalbreath, a nitpick would be that protobuf@23:25 ^abseil-cpp@20260107.1 are building (at least with gcc@14 and gcc@16):

spack find protobuf@:29 +shared ^abseil-cpp@20260107.1
-- linux-ubuntu24.04-x86_64_v4 / %c,cxx=gcc@14.3.0 --------------
protobuf@23.3  protobuf@24.3  protobuf@25.3

-- linux-ubuntu24.04-x86_64_v4 / %c,cxx=gcc@16.0.1 --------------
protobuf@23.3  protobuf@24.3  protobuf@25.3
==> 6 installed packages

Below protobuf@23, there are older errors. Because these are older versions, I refrain from suggesting to add a special exception for them just to allow them to use ^abseil-cpp@20260107.1. I'd assume the older versions could be deprecated, but that would be separate discussion, I guess.

[bernhardkaindl]

Besides the approved conflict on abseil-cpp@20250512: for @:29, these are the gcc version conflicts I found:

    # GCC version limits of older protobuf versions:
    conflicts("%gcc@15:", when="@22.2 +shared")  # single release broken for gcc >= 15
    conflicts("%gcc@13:", when="@:3.2.0 +shared")
    conflicts("%gcc@11:", when="@:3.1.0 +shared")

They can be added in a separate PR of course and are for much older versions only. These are my 189 builds of protobuf grouped by compiler version, not every entry is covered, but the edges of what builds are covered (it's a wide table,

spack find protobuf # ("protobuf@" removed to not be a wide table):
-- linux-ubuntu24.04-x86_64_v4 / %c,cxx=gcc@10.5.0 --------------
3.0.2  3.1.0  3.2.0  3.3.0  3.4.0  3.4.1  3.5.0

-- linux-ubuntu24.04-x86_64_v4 / %c,cxx=gcc@11.5.0 --------------
3.5.0.1  3.5.2  3.7.1  3.9.2   3.11.0  3.11.3  3.12.1
3.5.1    3.6.1  3.8.0  3.10.0  3.11.1  3.11.4  3.12.3
3.5.1.1  3.7.0  3.9.1  3.10.1  3.11.2  3.12.0

-- linux-ubuntu24.04-x86_64_v4 / %c,cxx=gcc@12.4.0 --------------
3.3.0  3.4.1  3.5.0.1  3.5.1.1  3.6.1  3.14.0  3.15.1  21.12
3.4.0  3.5.0  3.5.1    3.5.2    3.7.0  3.15.0  3.15.2

-- linux-ubuntu24.04-x86_64_v4 / %c,cxx=gcc@13.3.0 --------------
3.3.0    3.9.1   3.11.3  3.14.0  3.15.4  3.18.0  3.20.2  21.7
3.4.0    3.9.2   3.11.4  3.15.0  3.15.4  3.18.2  3.20.3  21.9
3.4.1    3.10.0  3.12.0  3.15.0  3.15.5  3.19.2  21.1    21.12
3.5.0    3.10.1  3.12.1  3.15.1  3.15.7  3.19.3  21.2    21.12
3.5.0.1  3.11.0  3.12.2  3.15.1  3.16.0  3.19.4  21.3    22.2
3.5.1    3.11.1  3.12.3  3.15.2  3.17.0  3.20.0  21.4    22.2
3.8.0    3.11.2  3.13.0  3.15.2  3.17.3  3.20.1  21.5

-- linux-ubuntu24.04-x86_64_v4 / %c,cxx=gcc@14.3.0 --------------
3.3.0  3.4.1  21.12  23.3  25.3  33.1  34.1
3.4.0  21.9   22.2   24.3  33.0  34.0

-- linux-ubuntu24.04-x86_64_v4 / %c,cxx=gcc@15.2.0 --------------
3.3.0  3.4.0  3.4.1  21.4  21.5  21.7  21.9  21.12  28.2

-- linux-ubuntu24.04-x86_64_v4 / %c,cxx=gcc@16.0.1 --------------
3.3.0    3.7.0   3.11.2  3.15.4  3.19.3  21.4   25.3  32.1
3.4.0    3.7.1   3.11.3  3.15.5  3.19.4  21.5   25.3  33.0
3.4.1    3.8.0   3.11.4  3.15.7  3.20.0  21.7   26.1  33.1
3.5.0    3.9.1   3.12.0  3.16.0  3.20.1  21.9   27.5  34.0
3.5.0.1  3.9.2   3.12.1  3.17.0  3.20.2  21.12  28.2  34.1
3.5.1    3.10.0  3.12.2  3.17.3  3.20.3  23.3   28.3
3.5.1.1  3.10.1  3.15.0  3.18.0  21.1    23.3   29.3
3.5.2    3.11.0  3.15.1  3.18.2  21.2    24.3   30.2
3.6.1    3.11.1  3.15.2  3.19.2  21.3    24.3   31.1

-- linux-ubuntu24.04-x86_64_v4 / %c,cxx=rocmcc@7.2.3 ------------
3.12.2  3.13.0
==> 189 installed packages

[zackgalbreath]

protobuf@23:25 ^abseil-cpp@20260107.1 are building (at least with gcc@14 and gcc@16):

You're right, thanks for pointing this out. I took a closer look and I found that protobuf v26 - v29 link against absl::if_constexpr. I updated this PR accordingly.

[bernhardkaindl]

Ack, approved, no further concerns from my side.

As a hint: With other errors (I guess related to not supported cxxstd or so), versions below 23 ("protobuf@:22") also don't compile with ^abseil-cpp@20260107.1 (maybe related: the abseil-cpp recipe sets cxxstd=17 for it) - at least with the gcc version (14 or 16) I used. I assume these might be candidates for deprecation, but I leave that to the experts. 👍