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Check for NULL from proj_as_proj_string in proj_factors derived CRS handling #4705

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Check for NULL from proj_as_proj_string in proj_factors derived CRS handling #4705

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612a8d5
Fix null handling in proj_factors derived CRS path
ClayWarren Mar 7, 2026
e9a4514
Update src/factors.cpp
ClayWarren Mar 7, 2026
7bc9aa8
Merge pull request #1 from ClayWarren/codex/propose-fix-for-null-dere…
ClayWarren Mar 7, 2026
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13 changes: 11 additions & 2 deletions src/factors.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -257,8 +257,15 @@ PJ_FACTORS proj_factors(PJ *P, PJ_COORD lp) {
proj_destroy(cs);

// Remove trailing unit conversion and axis swap
std::string osProjStr =
const char *pszProjStr =
proj_as_proj_string(ctx, newOp, PJ_PROJ_5, nullptr);
if (!pszProjStr) {
proj_destroy(newOp);
if (horiz)
proj_destroy(horiz);
return factors;
}
std::string osProjStr = pszProjStr;
bool resized = false;
for (const char *suffix :
{" +step +proj=unitconvert", " +step +proj=axiswap"}) {
Expand All @@ -271,7 +278,9 @@ PJ_FACTORS proj_factors(PJ *P, PJ_COORD lp) {
if (resized) {
proj_destroy(newOp);
newOp = proj_create(ctx, osProjStr.c_str());
assert(newOp);
if (!newOp) {
return factors;
}
}

newOp->fr_meter = cs_unit_conv_factor;
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73 changes: 73 additions & 0 deletions test/unit/gie_self_tests.cpp
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Expand Up @@ -798,6 +798,79 @@ TEST(gie, proj_factors) {
proj_destroy(P);
}

// Test with a derived projected CRS that cannot be exported to PROJ string
{
PJ_COORD c;
c.lp.lam = proj_torad(9);
c.lp.phi = proj_torad(0);

const char *wkt =
"DERIVEDPROJCRS[\"unknown\",\n"
" BASEPROJCRS[\"unknown\",\n"
" BASEGEOGCRS[\"unknown\",\n"
" DATUM[\"Unknown based on WGS 84 ellipsoid\",\n"
" ELLIPSOID[\"WGS 84\",6378137,298.257223563,\n"
" LENGTHUNIT[\"metre\",1],\n"
" ID[\"EPSG\",7030]]],\n"
" PRIMEM[\"Greenwich\",0,\n"
" ANGLEUNIT[\"degree\",0.0174532925199433],\n"
" ID[\"EPSG\",8901]]],\n"
" CONVERSION[\"World Mercator\",\n"
" METHOD[\"Mercator (variant A)\",\n"
" ID[\"EPSG\",9804]],\n"
" PARAMETER[\"Latitude of natural origin\",1,\n"
" ANGLEUNIT[\"degree\",0.0174532925199433],\n"
" ID[\"EPSG\",8801]],\n"
" PARAMETER[\"Longitude of natural origin\",0,\n"
" ANGLEUNIT[\"degree\",0.0174532925199433],\n"
" ID[\"EPSG\",8802]],\n"
" PARAMETER[\"Scale factor at natural origin\",1,\n"
" SCALEUNIT[\"unity\",1],\n"
" ID[\"EPSG\",8805]],\n"
" PARAMETER[\"False easting\",0,\n"
" LENGTHUNIT[\"metre\",1],\n"
" ID[\"EPSG\",8806]],\n"
" PARAMETER[\"False northing\",0,\n"
" LENGTHUNIT[\"metre\",1],\n"
" ID[\"EPSG\",8807]]]],\n"
" DERIVINGCONVERSION[\"Identity\",\n"
" METHOD[\"Affine parametric transformation\",\n"
" ID[\"EPSG\",9624]],\n"
" PARAMETER[\"A0\",0,\n"
" LENGTHUNIT[\"metre\",1],\n"
" ID[\"EPSG\",8623]],\n"
" PARAMETER[\"A1\",1,\n"
" SCALEUNIT[\"coefficient\",1],\n"
" ID[\"EPSG\",8624]],\n"
" PARAMETER[\"A2\",0,\n"
" SCALEUNIT[\"coefficient\",1],\n"
" ID[\"EPSG\",8625]],\n"
" PARAMETER[\"B0\",0,\n"
" LENGTHUNIT[\"metre\",1],\n"
" ID[\"EPSG\",8639]],\n"
" PARAMETER[\"B1\",0,\n"
" SCALEUNIT[\"coefficient\",1],\n"
" ID[\"EPSG\",8640]],\n"
" PARAMETER[\"B2\",1,\n"
" SCALEUNIT[\"coefficient\",1],\n"
" ID[\"EPSG\",8641]]],\n"
" CS[Cartesian,2],\n"
" AXIS[\"easting (X)\",east,\n"
" ORDER[1],\n"
" LENGTHUNIT[\"metre\",1]],\n"
" AXIS[\"northing (Y)\",north,\n"
" ORDER[2],\n"
" LENGTHUNIT[\"metre\",1]]]";
P = proj_create(PJ_DEFAULT_CTX, wkt);
ASSERT_TRUE(P != nullptr);

factors = proj_factors(P, c);
EXPECT_NE(proj_errno(P), 0);
EXPECT_EQ(factors.meridional_scale, 0);

proj_destroy(P);
}

// Same as above but with foot unit
{
PJ_COORD c;
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